There are 771 twelve-letter words containing A, C, 2S and T, https://www.bestwordlist.com/c/a/5/12letterwordswithacsst.htm
ABJECTNESSES ABSOLUTISTIC ABSORPTANCES ABSTINENCIES ABSTRACTIONS
ABSTRACTIVES ABSTRACTNESS ABSTRICTIONS ACAROLOGISTS ACATALEPSIES
ACCLIMATISES ACCOMPANISTS ACCURATENESS ACHROMATISES ACHROMATISMS
ACOLOUTHOSES ACOUSTICIANS ACQUIESCENTS ACQUISITIONS ACTIVENESSES
ADDICTEDNESS ADSCITITIOUS ADSCRIPTIONS ADULTESCENTS AESTHETICISE
AESTHETICISM AESTHETICIST AFFECTEDNESS AGNOSTICISMS AHISTORICISM
ANACATHARSES ANACATHARSIS ANAESTHETICS ANCESTRESSES ANILINCTUSES
ANISODACTYLS ANTHRACNOSES ANTIFASCISMS ANTIFASCISTS ANTIMACASSAR
ANTISCIENCES ANTISPASTICS APOLITICISMS APOSTOLICISM ARTHROSCOPES
ARTOCARPUSES ASCENSIONIST ASCOMYCETOUS ASEPTICISING ASSOCIATIONS
ASSUEFACTION ASTACOLOGIES ASTACOLOGIST ASTRINGENCES ASTROCOMPASS
ASTROCYTOMAS ASTROHATCHES ASTRONAUTICS ASTROPHYSICS ATHLETICISMS
ATHROCYTOSES ATHROCYTOSIS ATMOSPHERICS AUSCULTATORS BACKSCATTERS
BACKSTABBERS BACKSTITCHES BACKSTROKERS BATHYSCAPHES BATTLESPACES
BENEFACTRESS BICUSPIDATES BIOACOUSTICS BIOCATALYSES BIOCATALYSIS
BIOCATALYSTS BISOCIATIONS BLACKLISTERS BLASTOCHYLES BLASTOCOELES
BROADCASTERS CACTOBLASTES CACTOBLASTIS CAESPITOSELY CALENDARISTS
CALISTHENICS CALLISTEMONS CANDLESTICKS CANISTERISED CANISTERISES
CANISTERIZES CANOPHILISTS CAPSULATIONS CAPTAINSHIPS CAPTIOUSNESS
CARILLONISTS CARPOLOGISTS CASHIERMENTS CASSITERITES CASTIGATIONS
CATACAUSTICS CATACOUSTICS CATALOGUISES CATALOGUISTS CATAPHORESES
CATAPHORESIS CATASTROPHES CATCHINESSES CATCHPHRASES CATECHESISES
CATECHISINGS CATHETERISES CATHETERISMS CATHOLICISES CATHOLICISMS
CATHOLICOSES CAUSATIONISM CAUSATIONIST CAUSTICITIES CAUTIOUSNESS
CENESTHESIAS CENTRALISERS CEPHALITISES CERATOPSIANS CEREBRALISTS
CEROPLASTICS CHALKSTRIPES CHANSONETTES CHARGESHEETS CHARISMATICS
CHASTENESSES CHASTENMENTS CHASTISEMENT CHATTINESSES CHAUNTRESSES
CHEATGRASSES CHEESESTEAKS CHEESETASTER CHEMONASTIES CHEMOTAXISES
CHIASTOLITES CHIEFTAINESS CHLOROPLASTS CHOIRMASTERS CHORISATIONS
CHORUSMASTER CHRISMATIONS CHRISTIANIAS CHROMOPLASTS CIRROSTRATUS
CLARINETISTS CLASSICALIST CLASSICALITY CLASSICISTIC CLAVECINISTS
CLEARSTORIES CLERICALISTS CLICKSTREAMS CLISTOGAMIES COASTEERINGS
COENESTHESIA COLONIALISTS COMMISERATES COMMISSARIAT COMMUNALISTS
COMPARATISTS COMPENSATORS CONFISCATORS CONSECRATORS CONSECTARIES
CONSERVATISE CONSERVATISM CONSERVATORS CONSISTORIAL CONSISTORIAN
CONSOLATIONS CONSOLIDATES CONSPIRACIST CONSPIRATORS CONSTELLATES
CONSTERNATES CONSTRAINERS CONSTUPRATES CONSUMMATORS CONTRABASSES
CONTRABASSOS CONTRABBASSI CONTRABBASSO CONTRARINESS CONTRASTIEST
CONTREDANSES CORNSTARCHES CORPORATISES CORPORATISMS CORPORATISTS
CORUSCATIONS CORYBANTISMS COSCENARISTS COSMETICIANS COSMOLATRIES
COSMONAUTICS COSMOPLASTIC COTONEASTERS COTRANSDUCES COTRANSPORTS
COUNTERBASES COUNTERSEALS COUNTRYSEATS CRAFTINESSES CRAFTSPERSON
CRAPSHOOTERS CRASSAMENTUM CREATIANISMS CREATIONISMS CREATIONISTS
CREATIVENESS CREATORSHIPS CRESCENTADES CRETACEOUSES CRIMINALISTS
CRITICALNESS CRITICASTERS CROSSABILITY CROSSHATCHED CROSSHATCHES
CROSSMATCHED CROSSMATCHES CROSSPATCHES CRYSTALISERS CRYSTALISING
CRYSTALIZERS CRYSTALLINES CRYSTALLISED CRYSTALLISER CRYSTALLISES
CRYSTALLITES CRYSTALLITIS CRYSTALLIZES CRYSTALLOIDS CURATIVENESS
CURATORSHIPS CUSPIDATIONS CUSTOMISABLE CYCLISATIONS DECAPSULATES
DECARTELISES DECRETALISTS DECUSSATIONS DELICATENESS DELICATESSEN
DEMOCRATISES DEMOCRATISTS DESANCTIFIES DESECRATIONS DESICCATIONS
DESICCATIVES DETACHEDNESS DEUTSCHMARKS DIATONICISMS DIBASICITIES
DICTATRESSES DIDACTICISMS DIDACTYLISMS DISACCREDITS DISACCUSTOMS
DISASSOCIATE DISCALCEATES DISCARDMENTS DISCEPTATORS DISCONSOLATE
DISENTRANCES DISLOCATIONS DISSOCIALITY DISSOCIATING DISSOCIATION
DISSOCIATIVE DISTANCELESS DISTRACTIONS DISTURBANCES DOCKISATIONS
DODECASTYLES DOMESTICATES DRACONTIASES DRACONTIASIS DRAMATICISMS
DYNASTICISMS DYSAESTHETIC ECCLESIASTIC EDUCATEDNESS ELASTICISING
ELASTICITIES EMASCULATORS ENCAPSULATES ENCYSTATIONS ENTHUSIASTIC
ESCAPOLOGIST ESCHEATMENTS ESTHETICIANS EUCALYPTUSES EVISCERATORS
EXACTINGNESS EXPISCATIONS EXSICCATIONS EXTRINSICALS FACSIMILISTS
FACTIOUSNESS FANTASTICISM FANTASTICOES FASCINATIONS FISSICOSTATE
FORECASTINGS FORNICATRESS FRACTIONISES GALACTOSIDES GASTRONOMICS
GASTROSCOPES GASTROSCOPIC GASTROTRICHS GATECRASHERS GESELLSCHAFT
GESTICULATES GIGANTICNESS GLASSCUTTERS GLOSSEMATICS GLYCOSYLATES
GRACIOSITIES GYNAECOMASTS HAEMOSTATICS HARMONICISTS HARUSPICATES
HEPTARCHISTS HETEROSCIANS HEXASTICHONS HUCKSTERAGES HYDROSTATICS
HYPAESTHESIC ICHTHYOSAURS INACTIVENESS INCAPSULATES INCENSATIONS
INCHOATENESS INCRASSATING INCRASSATION INCRASSATIVE INOSILICATES
INSECTARIUMS INTACTNESSES INTERCLASSES INTERCOSTALS INTRASPECIES
IRRESISTANCE ISOMAGNETICS JUSTICIALISM JUSTICIARIES KETOACIDOSES
KETOACIDOSIS KINESIATRICS LACTESCENCES LACUNOSITIES LAICISATIONS
LANDSCAPISTS LANDSKNECHTS LATCHSTRINGS LECITHINASES LINECASTINGS
LOGISTICIANS LOGOMACHISTS MACKINTOSHES MACROCYTOSES MACROCYTOSIS
MAGISTRACIES MAJESTICNESS MALEFACTRESS MARCATISSIMO MASCULINISTS
MASTECTOMIES MASTERPIECES MASTICATIONS MESOTHORACES METACARPUSES
METAPSYCHICS MINICASSETTE MISALLOCATES MISCANTHUSES MISCEGENATES
MISCELLANIST MISCHANCIEST MISCITATIONS MISCREATIONS MISLOCATIONS
MONASTICISMS MONOCRYSTALS MUSCULATIONS MUSCULATURES MUSICALITIES
MYCOPHAGISTS MYSTICALNESS NANOCRYSTALS NARCISSISTIC NECESSITATED
NECESSITATES NEWSCASTINGS NIGHTCLASSES NONCONSTANTS NONSOCIALIST
NYCTINASTIES OBFUSCATIONS OBSCURANTISM OBSCURANTIST OBSCURATIONS
OBSECRATIONS OCTASTICHONS OCTASTICHOUS OCTOSEPALOUS ONOMASTICONS
ORCHESTRATES ORCHESTRINAS OSCILLATIONS OSCULATORIES OSSIFICATION
OSTEOBLASTIC OSTEOCLASTIC OSTEOPLASTIC OSTEOSARCOMA OSTRACISABLE
OSTRACODERMS OUTDISTANCES OVERCASTINGS PACESETTINGS PANCRATIASTS
PANPSYCHISTS PANTISOCRATS PARACENTESES PARACENTESIS PARACHUTISTS
PARACROSTICS PARASTICHIES PARASTICHOUS PATCHINESSES PATRISTICISM
PECTISATIONS PEDANTICISES PEDANTICISMS PESCATARIANS PESCETARIANS
PETTICHAPSES PHAGOCYTISES PHAGOCYTISMS PHAGOCYTOSES PHAGOCYTOSIS
PHOTOMOSAICS PHYSICALISTS PLASTICISERS PLASTICISING PLASTICITIES
PLASTICIZERS PLASTICKIEST PLASTICWARES POETICALNESS POLYCRYSTALS
POSTORGASMIC POSTSURGICAL POSTSYNAPTIC POSTULANCIES PRECISIANIST
PRIESTCRAFTS PSYCHIATRIES PSYCHIATRIST PUNCTUALISTS PYROCLASTICS
QUASICRYSTAL REACTIONISMS REACTIONISTS REACTIVENESS REBROADCASTS
RESEARCHISTS RESPECTABLES RESUSCITABLE RESUSCITANTS RESUSCITATED
RESUSCITATES RESUSCITATOR RHAPSODISTIC ROCKSTEADIES ROMANTICISES
ROMANTICISMS ROMANTICISTS ROUGHCASTERS RUSTICATINGS RUSTICATIONS
SABERMETRICS SACCULATIONS SACRAMENTALS SACRILEGISTS SACROCOSTALS
SACROILIITIS SADDLECLOTHS SADISTICALLY SALTCHUCKERS SALTIMBANCOS
SALTIMBOCCAS SANCTIFYINGS SANCTIMONIES SANCTIONEERS SANCTIONINGS
SANCTIONLESS SANCTUARISED SANCTUARISES SANCTUARIZES SANSCULOTTES
SANSCULOTTIC SANTALACEOUS SARCOMATOSES SARCOMATOSIS SATISFACTION
SATISFACTORY SATISFICINGS SCABRIDITIES SCAMBAITINGS SCANTINESSES
SCAPEGOATISM SCARABAEISTS SCATOLOGISTS SCATOPHAGIES SCATOPHAGOUS
SCATTERGOODS SCATTERGRAMS SCATTERLINGS SCATTINESSES SCHECKLATONS
SCHEMATISING SCHISMATICAL SCHISMATISED SCHISMATISES SCHISMATIZED
SCHISMATIZES SCHISTOSOMAL SCHMALTZIEST SCHOLARLIEST SCHOLASTICAL
SCHOOLCRAFTS SCHOOLMASTER SCINTILLATES SCISSIPARITY SCISSORTAILS
SCITAMINEOUS SCOUTMASTERS SCRATCHBACKS SCRATCHCARDS SCRATCHINESS
SCREENCRAFTS SCYPHISTOMAE SCYPHISTOMAS SEARCHLIGHTS SECRETARIATS
SECTARIANISE SECTARIANISM SECTIONALISE SECTIONALISM SECTIONALIST
SECULARISTIC SECULARITIES SEISMONASTIC SELECTORATES SEMANTICISTS
SEMIABSTRACT SEMICOMATOSE SEMIMONASTIC SEMIMYSTICAL SEMIOTICIANS
SENSUALISTIC SEPARATISTIC SEPARATRICES SEPTICAEMIAS SHADOWCASTED
SHORTCHANGES SIDEROSTATIC SIGNIFICANTS SIGNIFICATES SIMULCASTING
SINGLETRACKS SLACKTIVISMS SLACKTIVISTS SMALLCLOTHES SMARTWATCHES
SOCIOPATHIES SOLECISTICAL SOLIDARISTIC SOMAESTHETIC SOMATOTENSIC
SOMATOTONICS SOPHISTICATE SPACEFLIGHTS SPACIALITIES SPASMOLYTICS
SPASTICITIES SPATTERDOCKS SPECIALISTIC SPECIALITIES SPECIFICATES
SPECTACULARS SPECTATRICES SPECTATRIXES SPECTRALNESS SPECTROGRAMS
SPECULATIONS SPECULATISTS SPEECHCRAFTS SPERMATHECAS SPHRAGISTICS
SPICULATIONS SPIFFLICATES SPIROCHAETES SPORTCASTERS SPORTSCASTER
STACTOMETERS STAGECOACHES STAIRCASINGS STANCHNESSES STARCHEDNESS
STARFUCKINGS STATISTICIAN STAUROSCOPES STAUROSCOPIC STAYSTITCHED
STAYSTITCHES STEEPLECHASE STEEPLEJACKS STEGOCARPOUS STENOCARDIAS
STEPDANCINGS STERCORANISM STERCORANIST STERCORARIES STERNOCOSTAL
STICKHANDLES STICKLEADERS STICKLEBACKS STIMULANCIES STIPULACEOUS
STITCHCRAFTS STOCKTAKINGS STOMACHACHES STRABISMICAL STREETSCAPES
STRETCHMARKS STRIDULANCES STYRACACEOUS SUBACIDITIES SUBALLOCATES
SUBAPOSTOLIC SUBCELESTIAL SUBCONTRACTS SUBCUTANEOUS SUBFACULTIES
SUBINDICATES SUBSECRETARY SUBSPECIALTY SUBSTRACTING SUBSTRACTION
SUBSTRACTORS SUBTENANCIES SUBTRACTIONS SUCCESSANTLY SUCCUSSATION
SUFFOCATINGS SUFFOCATIONS SUPERELASTIC SUPEROCTAVES SUPERPLASTIC
SUPPLICAVITS SUPPORTANCES SUPRACRUSTAL SUPREMACISTS SURFCASTINGS
SURREALISTIC SUSCEPTANCES SUSCITATIONS SUSTENTACULA SWITCHBLADES
SWITCHBOARDS SYCOPHANTISE SYCOPHANTISH SYCOPHANTISM SYLLABICATES
SYMPATHETICS SYNAESTHETIC SYNCOPATIONS SYNDACTYLIES SYNDACTYLISM
SYNDACTYLOUS SYNDICALISTS SYNDICATIONS SYSTEMATICAL SYSTEMICALLY
TACHYPHASIAS TACTLESSNESS TEACHERSHIPS TECHNOSPEAKS TERSANCTUSES
TESTIFICATES THALASSAEMIC THALASSEMICS THALASSOCRAT THEATRICISES
THEATRICISMS THEOMACHISTS THOUGHTCASTS TOBACCONISTS TOSTICATIONS
TOWNSCAPINGS TOXOCARIASES TOXOCARIASIS TRACASSERIES TRACHEITISES
TRAGICALNESS TRANSACTIONS TRANSCEIVERS TRANSCRIBERS TRANSDUCTORS
TRANSECTIONS TRANSIENCIES TRANSLOCATES TRANSPICUOUS TRANSPIERCES
TRANSURANICS TRICHINIASES TRICHINIASIS TRICHURIASES TRICHURIASIS
TRITICALNESS TROPICALISES TRUCKMASTERS TSAREVITCHES TSESAREVITCH
TSESAREWITCH TYPECASTINGS UNASSOCIATED UNCHASTENESS UNCHASTITIES
UNCHRISTIANS UNSANCTIFIES UNSECTARIANS UNSYSTEMATIC VACANTNESSES
VACATIONISTS VACATIONLESS VARICOSITIES VASCULATURES VASCULITIDES
VASCULITISES VASECTOMISED VASECTOMISES VASECTOMIZES VERTICALNESS
VESICATORIES VINDICATRESS VISCOELASTIC VULCANISATES WAINSCOTINGS
WATCHFULNESS WATCHGLASSES WATCHSPRINGS WATERCOURSES WATERCRESSES
WEATHERCASTS WELWITSCHIAS WITCHGRASSES WRECKMASTERS WRISTWATCHES
ZYGOCACTUSES