There are 783 fifteen-letter words containing A, C and 2S, https://www.bestwordlist.com/c/a/4/15letterwordswithacss.htm
ABSORBEFACIENTS ABSTRACTIONISMS ABSTRACTIONISTS ACCEPTINGNESSES
ACCESSARINESSES ACCESSIBILITIES ACCESSORINESSES ACCOMPLISHMENTS
ACCOUNTABLENESS ACCOUNTANTSHIPS ACHONDROPLASIAS ACQUISITIVENESS
ACRIMONIOUSNESS ACROPARESTHESIA ADDICTIVENESSES AERODYNAMICISTS
AEROELASTICIANS AFFECTIVENESSES AGRANULOCYTOSES AGRANULOCYTOSIS
ALCOHOLISATIONS ALLEGORICALNESS ANAMORPHOSCOPES ANCYLOSTOMIASES
ANCYLOSTOMIASIS ANDROMONOECISMS ANFRACTUOSITIES ANTAPHRODISIACS
ANTIALCOHOLISMS ANTICAPITALISMS ANTICAPITALISTS ANTICONVULSANTS
ANTICONVULSIVES ANTIHISTAMINICS ANTIMONARCHISTS ANTINEOPLASTICS
ANTINUCLEARISTS ANTIPHLOGISTICS ANTIRADICALISMS ANTISEPTICISING
ANTISOCIALITIES ANTISYPHILITICS APOCALYPTICISMS APPRENTICESHIPS
ARACHNOIDITISES ARCHAEOMETRISTS ARCHEOBOTANISTS ARCHPRIESTHOODS
ARCHPRIESTSHIPS ASCLEPIADACEOUS ASSOCIABILITIES ASSOCIATIONISMS
ASSOCIATIONISTS ASSOCIATIVITIES ASTRODYNAMICIST ASTROPHYSICALLY
ASTROPHYSICISTS ATHEROSCLEROSES ATHEROSCLEROSIS ATROCIOUSNESSES
AUDACIOUSNESSES AUTOSCHEDIASTIC BACKSCATTERINGS BACKSCRATCHINGS
BACTERIOLOGISTS BAREFACEDNESSES BASIDIOMYCETOUS BIDIALECTALISMS
BIOACOUSTICIANS BIOASTRONAUTICS BIOSTATISTICIAN BLOCKHEADEDNESS
BRACHIOSAURUSES BRAINSICKNESSES BRAUNSCHWEIGERS CANISTERISATION
CAPACIOUSNESSES CAPITALISATIONS CARAMELISATIONS CARCINOSARCOMAS
CARNIVOROUSNESS CASTANOSPERMINE CASTRAMETATIONS CATECHUMENSHIPS
CATEGORICALNESS CATEGORISATIONS CAUSATIVENESSES CAUSELESSNESSES
CEASELESSNESSES CENSURABILITIES CENTENARIANISMS CENTRALISATIONS
CENTRICALNESSES CENTRIFUGALISES CENTRIPETALISMS CHALCOGRAPHISTS
CHANCELLORSHIPS CHANGEFULNESSES CHANNELISATIONS CHAPTALISATIONS
CHARACTERISTICS CHEMOTHERAPISTS CHLORITISATIONS CHOLESTYRAMINES
CHOLINESTERASES CHORDAMESODERMS CHROMATICNESSES CHROMATOLOGISTS
CHROMATOSPHERES CINCHONISATIONS CIRCUMSTANTIALS CLAMOROUSNESSES
CLANDESTINENESS CLANDESTINITIES CLASSICALNESSES CLASSIFICATIONS
CLASSLESSNESSES CLAUSTROPHILIAS CLAUSTROPHOBIAS CLEARHEADEDNESS
CLEAVABLENESSES CLEISTOGAMOUSLY COCHAIRMANSHIPS COESSENTIALNESS
COINSTANTANEOUS COINVESTIGATORS COLDHEARTEDNESS COLONISATIONIST
COLORABLENESSES COLORFASTNESSES COMBATIVENESSES COMFORTABLENESS
COMMANDANTSHIPS COMMENDABLENESS COMMENSURATIONS COMMISSARYSHIPS
COMMISSIONAIRES COMMONPLACENESS COMPACTEDNESSES COMPARATIVENESS
COMPASSIONATELY COMPASSIONATING COMPLIANTNESSES COMPLICATEDNESS
COMRADELINESSES CONCEIVABLENESS CONCEPTUALISERS CONCESSIONAIRES
CONCESSIONARIES CONCESSIONNAIRE CONCRETISATIONS CONFESSIONALISM
CONFESSIONALIST CONFESSIONARIES CONFORMABLENESS CONFUSABILITIES
CONGEALABLENESS CONGENIALNESSES CONGRESSIONALLY CONJUGATENESSES
CONQUERABLENESS CONSANGUINITIES CONSECRATEDNESS CONSENTANEITIES
CONSENTANEOUSLY CONSERVATIONIST CONSERVATORIUMS CONSERVATORSHIP
CONSIDERATENESS CONSIMILARITIES CONSPIRATRESSES CONSTITUTIONALS
CONSUBSTANTIATE CONSULTANTSHIPS CONTESSERATIONS CONTESTABLENESS
CONTINENTALISMS CONTINENTALISTS CONTINUALNESSES CONTRACTIVENESS
CONTRAPOSITIONS CONTRAPOSITIVES CONTRARIOUSNESS CONVALESCENCIES
CONVERSABLENESS CONVERSATIONISM CONVERSATIONIST CONVOCATIONISTS
CONVULSIONARIES COOPERATIONISTS COOPERATIVENESS CORPORATENESSES
CORPOREALNESSES CORPUSCULARIANS CORRELATIVENESS COSMOPOLITANISM
COTRANSDUCTIONS COUNTERASSAULTS COUNTERMEASURES COUNTERSHADINGS
CRAPULOUSNESSES CRASHWORTHINESS CRESTFALLENNESS CROSSOPTERYGIAN
CRUCIVERBALISMS CRUCIVERBALISTS CRYPTAESTHESIAS CRYPTOGRAPHISTS
CRYSTALISATIONS CRYSTALIZATIONS CRYSTALLINITIES CRYSTALLISATION
CUSTOMARINESSES CYBERSQUATTINGS CYCLOOXYGENASES CYLINDRICALNESS
CYTOTAXONOMISTS DEBAUCHEDNESSES DECASUALISATION DECHRISTIANISED
DECHRISTIANISES DECHRISTIANIZES DECIMALISATIONS DECOLONISATIONS
DECOLORISATIONS DECOMPENSATIONS DECONSECRATIONS DELOCALISATIONS
DESACRALISATION DESPICABILITIES DIALECTOLOGISTS DICHROMATICISMS
DICTATORIALNESS DIFFRACTIVENESS DISACCHARIDASES DISACCOMMODATES
DISACKNOWLEDGES DISAFFECTEDNESS DISAPPLICATIONS DISARTICULATORS
DISASSOCIATIONS DISCIPLINARIANS DISCIPLINARIUMS DISCOLOURATIONS
DISCOMBOBERATES DISCOMBOBULATES DISCONSOLATIONS DISCONTINUANCES
DISCOUNTENANCES DISCOURAGEMENTS DISCRIMINATIONS DISENCHANTMENTS
DISENCUMBRANCES DISENFRANCHISED DISENFRANCHISES DISGRACEFULNESS
DISINCARCERATES DISINCLINATIONS DISINCORPORATES DISINHERITANCES
DISSATISFACTION DISSATISFACTORY DISSOCIABLENESS DODECASYLLABLES
DOLICHOSAURUSES DYSLOGISTICALLY ECCLESIASTICISM ECCLESIOLATRIES
ECCREMOCARPUSES ECLAIRCISSEMENT ECOCATASTROPHES EDUCATIONALISTS
EFFECTUALNESSES EFFICACIOUSNESS ELECTROANALYSES ELECTROANALYSIS
ELECTRODIALYSES ELECTRODIALYSIS EMBRACINGNESSES EMPIRICALNESSES
EMULSIFICATIONS ENCYCLOPAEDISMS ENCYCLOPAEDISTS EPISCOPALIANISM
EQUIVOCALNESSES ESEMPLASTICALLY ESOPHAGOSCOPIES ESTERIFICATIONS
EVANGELICALISMS EVANGELICALNESS EVOCATIVENESSES EXACERBESCENCES
EXCEPTIONALISMS EXCEPTIONALISTS EXCEPTIONALNESS EXCITABLENESSES
EXCLAUSTRATIONS EXCUSABLENESSES EXECRABLENESSES FACETIOUSNESSES
FANATICALNESSES FANATICISATIONS FANTASTICALNESS FANTASTICATIONS
FEATHERSTITCHES FETISHISTICALLY FICTIONISATIONS FIDEICOMMISSARY
FORENSICALITIES FRACTIOUSNESSES FUGACIOUSNESSES FURACIOUSNESSES
GLOSSOGRAPHICAL GRACELESSNESSES GRAMMATICALNESS GRAMMATICASTERS
GRAPHICALNESSES HARPSICHORDISTS HEARTSICKNESSES HEMOCHROMATOSES
HEMOCHROMATOSIS HEPATICOLOGISTS HERESTHETICIANS HETEROSCEDASTIC
HIERACOSPHINGES HIERACOSPHINXES HOMOCHROMATISMS HOMOSOCIALITIES
HYDROCEPHALUSES HYPOCHONDRIASES HYPOCHONDRIASIS HYPOCHONDRIASMS
HYPOCHONDRIASTS ICHTHYOPHAGISTS ICHTHYOSAURIANS ICHTHYOSAURUSES
IDENTICALNESSES IDIOMATICALNESS IDIOMATICNESSES IDIOTICALNESSES
ILLOGICALNESSES IMMEDICABLENESS IMPLICATIVENESS IMPRACTICALNESS
IMPROVISATRICES INACCESSIBILITY INCANDESCENCIES INCAPABLENESSES
INCAPACIOUSNESS INCESSANTNESSES INCREMENTALISMS INCREMENTALISTS
INCURABLENESSES INEFFECTUALNESS INEXCUSABLENESS INFRASTRUCTURES
INSCRIBABLENESS INSCRUTABLENESS INSIGNIFICANCES INSOCIABILITIES
INTERACTIONISMS INTERACTIONISTS INTERSCHOLASTIC INTERSECTIONALS
INTRACTABLENESS INTRANSIGEANCES INTRANSIGENCIES INTRICATENESSES
INTRINSICALNESS IRASCIBLENESSES IRREVOCABLENESS ISMATICALNESSES
ISOTHIOCYANATES KAFFEEKLATSCHES KARSTIFICATIONS LACTIFEROUSNESS
LARYNGOSCOPISTS LEUCAEMOGENESES LEUCAEMOGENESIS LEXICALISATIONS
LEXICOGRAPHISTS LICENTIATESHIPS LISSENCEPHALIES LISSENCEPHALOUS
LUCRATIVENESSES MACADAMISATIONS MACROSTRUCTURES MAGNIFICENTNESS
MALICIOUSNESSES MASCULINENESSES MASCULINISATION MASOCHISTICALLY
MASTOIDECTOMIES MATCHLESSNESSES MATRIARCHALISMS MEDICALISATIONS
MENISPERMACEOUS MERCENARINESSES MERCURIALNESSES MESATICEPHALIES
MESATICEPHALOUS METACHROMATISMS METAFICTIONISTS METALINGUISTICS
METAPHYSICISING MICROAGGRESSION MICROAGGRESSIVE MICROAGGRESSORS
MICROPULSATIONS MICROSATELLITES MISACCEPTATIONS MISAPPLICATIONS
MISCALCULATIONS MISCELLANARIANS MISCELLANEOUSLY MISCHARACTERISE
MISCOMPUTATIONS MISCORRELATIONS MISGOVERNAUNCES MISPUNCTUATIONS
MISTRANSCRIBING MISVOCALISATION MONOCHROMATISMS MONOSACCHARIDES
MUCOSANGUINEOUS MULTIRACIALISMS MUSCULOSKELETAL MUSICALISATIONS
MUSICALIZATIONS MUSICOTHERAPIES NARCOTERRORISMS NARCOTERRORISTS
NECESSARIANISMS NECESSARINESSES NEOCOLONIALISMS NEOCOLONIALISTS
NEOCONSERVATISM NONCHARISMATICS NONCONSENSUALLY NONELASTICITIES
NONPSYCHIATRIST NONSENSICALNESS NONSIGNIFICANTS NONSPECTACULARS
NUCLEARISATIONS OCCASIONALITIES OESOPHAGOSCOPES OMOPLATOSCOPIES
OPHTHALMOSCOPES OPSONIFICATIONS ORACULOUSNESSES ORCHESOGRAPHIES
OSCILLOGRAPHIES OSTEOARTHRITICS OVERCAPITALISES OVERCENTRALISES
OVERCLASSIFYING OVERCOMPENSATES OVERSPECIALISED OVERSPECIALISES
OVERSPECIALIZES OXIDOREDUCTASES PALEOECOLOGISTS PANTISOCRATISTS
PARADOXICALNESS PARALINGUISTICS PARASITICALNESS PARTICULARISERS
PASSIFLORACEOUS PATRIARCHALISMS PEACEABLENESSES PEACELESSNESSES
PECTINESTERASES PENTADACTYLISMS PERIPATETICISMS PERISSODACTYLES
PERISSODACTYLIC PERISSOSYLLABIC PERSPICACIOUSLY PESSIMISTICALLY
PHALLOCENTRISMS PHARISAICALNESS PHARMACOGNOSIES PHARMACOGNOSIST
PHARMACOLOGISTS PHARMACOPOEISTS PHARMACOPOLISTS PHARYNGOSCOPIES
PHENAKISTOSCOPE PHOSPHOCREATINS PHOTODISSOCIATE PHYLLOSILICATES
PICTORIALNESSES PINEALECTOMISES PLACELESSNESSES PLASTICISATIONS
PLASTICIZATIONS POCOCURANTEISMS POLITICISATIONS POLYCHROMATISMS
POLYSACCHARIDES POLYSACCHAROSES POLYSYLLABICISM POSTADOLESCENCE
POSTADOLESCENTS POSTAPOCALYPSES POSTCONSONANTAL POSTSECONDARIES
PRACTICABLENESS PRACTICALNESSES PRAGMATICALNESS PREADOLESCENCES
PREANAESTHETICS PRECIPITANTNESS PRECIPITATENESS PREDICTABLENESS
PREJUDICIALNESS PRINCIPALNESSES PROCELEUSMATICS PROCESSIONALIST
PROCESSIONARIES PROCRASTINATORS PROCREATIVENESS PROCURATORSHIPS
PROGNOSTICATORS PROJECTISATIONS PROSAICALNESSES PROSENCHYMATOUS
PROSTATECTOMIES PROTOCERATOPSES PROVOCATIVENESS PSYCHOACOUSTICS
PSYCHOANALYSERS PSYCHOANALYSING PSYCHOANALYZERS PSYCHOCHEMICALS
PSYCHOHISTORIAN PSYCHOSEXUALITY PSYCHOTHERAPIES PSYCHOTHERAPIST
PUNCTUATIONISTS PURITANICALNESS QUADRISYLLABICS QUATTROCENTISMS
QUATTROCENTISTS RADICALISATIONS RANCOROUSNESSES RAPACIOUSNESSES
REACTIONARYISMS RECANALISATIONS RECOLONISATIONS RECONDENSATIONS
RECONNAISSANCES RECONNOISSANCES RECONSECRATIONS RECOVERABLENESS
RECRYSTALLISING REPROACHFULNESS RESECTABILITIES RESINIFICATIONS
RESOCIALISATION RESPECTABILISED RESPECTABILISES RESPECTABILIZES
RESPECTABLENESS RETROACTIVENESS REVOCABLENESSES ROSTROCARINATES
SABERMETRICIANS SACCHARIMETRIES SACCHARISATIONS SACCHARIZATIONS
SACCHAROMETRIES SACCHAROMYCETES SACERDOTALISING SACRAMENTALISMS
SACRAMENTALISTS SACRAMENTALNESS SACRAMENTARIANS SACROSANCTITIES
SADOMASOCHISTIC SAGACIOUSNESSES SALACIOUSNESSES SALPINGECTOMIES
SANCTIFICATIONS SANCTIMONIOUSLY SANGUIFICATIONS SANGUINOLENCIES
SANSCULOTTERIES SAPONACEOUSNESS SAPONIFICATIONS SAPROGENICITIES
SARCENCHYMATOUS SARRACENIACEOUS SATANICALNESSES SATIRICALNESSES
SCANDALISATIONS SCANDALIZATIONS SCAPHOCEPHALICS SCAPHOCEPHALIES
SCAPHOCEPHALISM SCAPHOCEPHALOUS SCAREMONGERINGS SCATHEFULNESSES
SCEUOPHYLACIUMS SCHEMATISATIONS SCHEMATIZATIONS SCHILLERISATION
SCHISTOSOMIASES SCHISTOSOMIASIS SCHOLARLINESSES SCHOOLMASTERING
SCHOOLMASTERISH SCHOOLTEACHINGS SCINTILLASCOPES SCLERODERMATOUS
SCLEROTHERAPIES SCLEROTISATIONS SCLEROTIZATIONS SCRATCHBUILDERS
SCRIBACIOUSNESS SCRIMSHANDERING SEARCHABILITIES SEARCHINGNESSES
SECONDARINESSES SECTIONISATIONS SECTIONIZATIONS SECULARISATIONS
SECULARIZATIONS SECURITISATIONS SECURITIZATIONS SEISMOGRAPHICAL
SEISMOLOGICALLY SEMIABSTRACTION SEMICENTENNIALS SEMICOLONIALISM
SEMICRYSTALLINE SEMITRANSLUCENT SERICITISATIONS SERICITIZATIONS
SEROPREVALENCES SERVICEABLENESS SERVOMECHANISMS SESQUICARBONATE
SESQUICENTENARY SHOCKUMENTARIES SILICIFICATIONS SIMPLIFICATIONS
SKEPTICALNESSES SKETCHABILITIES SOCIALISTICALLY SOCIOHISTORICAL
SOLIDIFICATIONS SOLIPSISTICALLY SOPHISTICATEDLY SOPHISTICATIONS
SPECIALISATIONS SPECIALIZATIONS SPECTROGRAPHIES SPECTROSCOPICAL
SPECULATIVENESS SPERMATOBLASTIC SPHAEROCRYSTALS SPHERICALNESSES
SPINTHARISCOPES SPIRONOLACTONES SPLANCHNOLOGIES STAPHYLOPLASTIC
STEEPLECHASINGS STEGOCEPHALIANS STOCKBROKERAGES STRAIGHTJACKETS
STRAITLACEDNESS STRAITWAISTCOAT STRATICULATIONS STRATIFICATIONS
STRATOSPHERICAL STRATOVOLCANOES STREPTOBACILLUS STREPTOCARPUSES
STRUCTURALISING STULTIFICATIONS SUBASSOCIATIONS SUBCATEGORISING
SUBCIVILISATION SUBCONTRACTINGS SUBMETACENTRICS SUBSPECIALISING
SUBSPECIALITIES SUBSPECIALIZING SUBSPECIFICALLY SUBVOCALISATION
SULPHACETAMIDES SUPERABUNDANCES SUPERACTIVITIES SUPERCARGOSHIPS
SUPERFICIALISED SUPERFICIALISES SUPERFICIALIZES SUPERFICIALNESS
SUPERORGANICISM SUPERORGANICIST SUPERPLASTICITY SUPERSPECIALIST
SUPERSPECTACLES SUPERSTRUCTURAL SUSPERCOLLATING SYLLOGISTICALLY
SYMBOLISTICALLY SYMMETRICALNESS SYMPATHECTOMIES SYNCHRONISATION
SYNCHRONISTICAL SYNCRETISATIONS SYNCRETIZATIONS SYNERGISTICALLY
TEACHABLENESSES TECHNICALNESSES TELANGIECTASIAS TENACIOUSNESSES
TERATOGENICISTS TETRABASICITIES THALASSOCRACIES THALASSOGRAPHIC
THEOSOPHISTICAL THICKHEADEDNESS THORACOCENTESES THORACOCENTESIS
THORACOPLASTIES TOUCHABLENESSES TRACEABLENESSES TRACKLESSNESSES
TRACTABLENESSES TRANSCENDENCIES TRANSCENDENTALS TRANSHISTORICAL
TRANSLUCIDITIES TRANSMITTANCIES TREACHEROUSNESS TRICHINISATIONS
TRISOCTAHEDRONS ULTRAPRECISIONS ULTRASTRUCTURES UNCANONICALNESS
UNCEASINGNESSES UNCERTAINNESSES UNCHRISTIANISED UNCHRISTIANISES
UNCHRISTIANIZES UNCLEANLINESSES UNCLIMBABLENESS UNCOMBATIVENESS
UNCOMPASSIONATE UNCONSENTANEOUS UNCREATEDNESSES UNEQUIVOCALNESS
UNMUSICALNESSES UNNECESSARINESS UNPEACEABLENESS UNPRACTICALNESS
UNPRACTISEDNESS UNSATISFACTIONS UNSECTARIANISMS UNSOCIABILITIES
UNSOPHISTICATED UNTACTFULNESSES UNTEACHABLENESS UNTRACTABLENESS
VASCULARISATION VASOCONSTRICTOR VERACIOUSNESSES VERTICILLASTERS
VICARIOUSNESSES VICISSITUDINARY VINDICATIVENESS VISCOELASTICITY
VISCOSIMETRICAL VIVACIOUSNESSES VORACIOUSNESSES WAPPENSCHAWINGS
WATERCOLOURISTS WELTANSCHAUUNGS WHIMSICALNESSES