There are 418 fifteen-letter words containing A, C, I, O and U, https://www.bestwordlist.com/c/a/5/15letterwordswithaciou.htm
ACCOUNTANTSHIPS ACCULTURATIONAL ACRIMONIOUSNESS AGRANULOCYTOSIS
ALUMINOSILICATE AMARYLLIDACEOUS ANACOLUTHICALLY ANDROMONOECIOUS
ANFRACTUOSITIES ANTICONVULSANTS ANTICONVULSIVES ANTIEDUCATIONAL
ANTIFORECLOSURE ANTISPECULATION ANTITUBERCULOUS ARBORICULTURIST
ASCLEPIADACEOUS ASTRONAUTICALLY ATROCIOUSNESSES AUDACIOUSNESSES
AUDIOMETRICALLY AUDIOMETRICIANS AUTHENTICATIONS AUTOCORRELATION
AUTODESTRUCTING AUTODESTRUCTIVE AUTODIDACTICISM AUTOGRAPHICALLY
AUTOINOCULATION AUTOMORPHICALLY AUTOSCHEDIASTIC AUTOSCHEDIAZING
AUTOTROPHICALLY BACTERIOPHAGOUS BASIDIOMYCETOUS BEAUTIFICATIONS
BIOACCUMULATING BIOACCUMULATION BIOACOUSTICIANS BIOASTRONAUTICS
BIOEQUIVALENCES BRACHIOSAURUSES CAPACIOUSNESSES CAPRIFOLIACEOUS
CARDIOPULMONARY CARNIVOROUSNESS CENTRIFUGATIONS CENTUPLICATIONS
CHEMAUTOTROPHIC CHENOPODIACEOUS CHONDROCRANIUMS CIRCULARISATION
CIRCULARIZATION CIRCUMAMBAGIOUS CIRCUMAMBULATOR CIRCUMFORANEOUS
CIRCUMGYRATIONS CIRCUMNAVIGATOR CIRCUMNUTATIONS CIRCUMVALLATION
CLAUSTROPHILIAS CLAUSTROPHOBIAS CLEISTOGAMOUSLY COAGULABILITIES
COEDUCATIONALLY COINSTANTANEOUS COLLOQUIALITIES COLOURABILITIES
COLOURISTICALLY COMMENSURATIONS COMMUNALISATION COMMUNALIZATION
COMMUNICABILITY COMMUNICATIONAL COMMUNICATIVELY COMMUNISTICALLY
COMMUTABILITIES COMMUTATIVITIES COMPUTABILITIES COMPUTATIONALLY
COMPUTERISATION COMPUTERIZATION COMPUTERPHOBIAS CONCEPTUALISERS
CONCEPTUALISING CONCEPTUALISTIC CONCEPTUALITIES CONCEPTUALIZERS
CONCEPTUALIZING CONDUPLICATIONS CONFIGURATIONAL CONFUSABILITIES
CONGLOBULATIONS CONGLUTINATIONS CONGRATULATIONS CONJUGATIONALLY
CONJUNCTIONALLY CONNATURALISING CONNATURALITIES CONNATURALIZING
CONSANGUINITIES CONSEQUENTIALLY CONSERVATORIUMS CONSTITUTIONALS
CONSUBSTANTIATE CONSULTANTSHIPS CONTEXTUALISING CONTEXTUALIZING
CONTINUALNESSES CONTRAPUNTALIST CONTRARIOUSNESS CONVULSIONARIES
CORPUSCULARIANS CORYNEBACTERIUM COTRANSDUCTIONS COULOMETRICALLY
COUNTERACTIVELY COUNTERADAPTIVE COUNTERCAMPAIGN COUNTERCHANGING
COUNTERCHARGING COUNTERCHARMING COUNTERCLAIMANT COUNTERCLAIMING
COUNTERCYCLICAL COUNTERFEISANCE COUNTERGUERILLA COUNTERINSTANCE
COUNTERINVASION COUNTERIRRITANT COUNTERMARCHING COUNTERPLANNING
COUNTERPLEADING COUNTERRALLYING COUNTERREACTION COUNTERSHADINGS
COUNTERSTAINING COUNTERVAILABLE CUSTOMARINESSES CYTOMEGALOVIRUS
DECARBURISATION DECARBURIZATION DECASUALISATION DECASUALIZATION
DECOLOURISATION DECOLOURIZATION DECOMMUNISATION DECOMMUNIZATION
DECONTEXTUALISE DECONTEXTUALIZE DEFLOCCULATIONS DEMULSIFICATION
DISARTICULATION DISARTICULATORS DISCOLOURATIONS DISCOMBOBULATED
DISCOMBOBULATES DISCONTINUANCES DISCONTINUATION DISCOUNTENANCED
DISCOUNTENANCES DISCOURAGEMENTS DOCUMENTARISING DOCUMENTARIZING
DOCUMENTATIONAL DOLICHOSAURUSES EBULLIOSCOPICAL EBURNIFICATIONS
ECHINODERMATOUS EDUCATIONALISTS EFFICACIOUSNESS ELECTROACOUSTIC
ELECTROSURGICAL EMULSIFICATIONS ENTEROBACTERIUM EQUIPONDERANCES
EQUIVOCALNESSES EUDAEMONISTICAL EUDIOMETRICALLY EUTROPHICATIONS
EXCLAUSTRATIONS EXCOMMUNICATING EXCOMMUNICATION EXCOMMUNICATIVE
EXCOMMUNICATORS EXCOMMUNICATORY FACETIOUSNESSES FLAVOURDYNAMICS
FRACTIOUSNESSES FRUCTIFICATIONS FUGACIOUSNESSES FUNCTIONALISTIC
FUNCTIONALITIES FURACIOUSNESSES GRANDILOQUENCES HAEMOGLOBINURIC
HALLUCINATIONAL HALLUCINOGENICS HAMAMELIDACEOUS HORTICULTURALLY
HUMIDIFICATIONS HYPERFUNCTIONAL ICHTHYOSAURIANS ICHTHYOSAURUSES
IMMUNOGENETICAL IMMUNOGENICALLY IMMUNOLOGICALLY IMMUNOREACTIONS
INARTICULATIONS INCAPACIOUSNESS INCOMMENSURABLE INCOMMENSURABLY
INCOMMUNICATIVE INCOMMUTABILITY INCOMPUTABILITY INCONSEQUENTIAL
INEFFICACIOUSLY INOCULABILITIES INSURRECTIONARY INTERJACULATORY
INTEROSCULATING INTEROSCULATION LACTIFEROUSNESS LEUCAEMOGENESIS
LEUCOCYTHAEMIAS LEUCOCYTOPENIAS LEUKOCYTOPENIAS LISSENCEPHALOUS
MACROEVOLUTIONS MACROPRUDENTIAL MACROSPORANGIUM MALFUNCTIONINGS
MALICIOUSNESSES MASCULINISATION MASCULINIZATION MENISPERMACEOUS
MERCAPTOPURINES MESATICEPHALOUS MICROEARTHQUAKE MICROPULSATIONS
MICROSPORANGIUM MICROSTRUCTURAL MINICALCULATORS MISARTICULATION
MISCALCULATIONS MISCELLANEOUSLY MISCOMPUTATIONS MISGOVERNAUNCES
MISPUNCTUATIONS MUCOSANGUINEOUS MULTIFUNCTIONAL MULTILOCATIONAL
MULTINUCLEOLATE MULTIPLICATIONS MUSICALISATIONS MUSICALIZATIONS
MUSICOLOGICALLY MUSICOTHERAPIES NEUROANATOMICAL NEUROBIOLOGICAL
NEUROPATHICALLY NEUROPATHOLOGIC NEUROPLASTICITY NEUROPSYCHIATRY
NEUROSURGICALLY NOCTAMBULATIONS NONAGRICULTURAL NONARCHITECTURE
NONCOMMUNICANTS NONCULTIVATIONS NONEQUIVALENCES NONFUNCTIONALLY
NONINTELLECTUAL NONMATRICULATED NONOCCUPATIONAL NUCLEARISATIONS
NUCLEARIZATIONS NUCLEOPLASMATIC OBSTRUCTIONALLY ORGANOMERCURIAL
OVERARTICULATED OVERARTICULATES OVERCOMMUNICATE OVERCULTIVATION
OVERENCOURAGING OVERSPECULATING OVERSPECULATION OXIDOREDUCTASES
PASSIFLORACEOUS PERSPICACIOUSLY PHONAUTOGRAPHIC PHOTODUPLICATED
PHOTODUPLICATES PITHECANTHROPUS PLANTAGINACEOUS PLUMBAGINACEOUS
PLUTOCRATICALLY PNEUMATOLOGICAL POCOCURANTEISMS POSTINOCULATION
PREPUBLICATIONS PROCELEUSMATICS PROCURATORSHIPS PRONUNCIAMENTOS
PRONUNCIATIONAL PSYCHOACOUSTICS PSYCHOSEXUALITY PULMOBRANCHIATE
PUNCTUATIONISTS QUADRUPLICATION QUANTIFICATIONS QUATTROCENTISMS
QUATTROCENTISTS QUINTUPLICATION QUIZZIFICATIONS QUODLIBETICALLY
RADICULOPATHIES RAPACIOUSNESSES REARTICULATIONS RECAPITULATIONS
RECONCEPTUALISE RECONCEPTUALIZE RECONFIGURATION RECONSTITUTABLE
RECONTEXTUALISE RECONTEXTUALIZE RESURRECTIONARY RHEUMATOLOGICAL
SAGACIOUSNESSES SALACIOUSNESSES SANCTIMONIOUSLY SANGUIFICATIONS
SANGUINOLENCIES SANSCULOTTERIES SARRACENIACEOUS SCEUOPHYLACIUMS
SCRIBACIOUSNESS SECULARISATIONS SECULARIZATIONS SECURITISATIONS
SECURITIZATIONS SEMIDOCUMENTARY SESQUICARBONATE SHOCKUMENTARIES
SOCIOCULTURALLY STRATICULATIONS STREPTOBACILLUS STULTIFICATIONS
SUBASSOCIATIONS SUBCATEGORISING SUBCATEGORIZING SUBCIVILISATION
SUBCIVILIZATION SUBCONTRACTINGS SUBVOCALISATION SUBVOCALIZATION
SUPERCARGOSHIPS SUPERORGANICISM SUPERORGANICIST SUSPERCOLLATING
TENACIOUSNESSES TENTACULIFEROUS TRAUMATOLOGICAL TUBERCULISATION
TUBERCULIZATION ULTRACOMMERCIAL ULTRACONVENIENT ULTRADEMOCRATIC
ULTRAMICROMETER ULTRAMICROSCOPE ULTRAMICROSCOPY ULTRAMICROTOMES
ULTRAPRECISIONS UNACCOMMODATING UNAPOSTOLICALLY UNAPPRECIATIONS
UNCANONICALNESS UNCATEGORISABLE UNCATEGORIZABLE UNCHRONOLOGICAL
UNCOMBATIVENESS UNCOMMUNICATIVE UNCOMPANIONABLE UNCOMPASSIONATE
UNCOMPLAININGLY UNCOMPLAISANTLY UNCOMPLIMENTARY UNCOMPROMISABLE
UNCONDITIONALLY UNCONSTRAINABLE UNCONSTRAINEDLY UNCONTROVERSIAL
UNCONVENTIONALS UNCOOPERATIVELY UNCOPYRIGHTABLE UNDOMESTICATING
UNEQUIVOCALNESS UNEXCEPTIONABLE UNEXCEPTIONABLY UNEXCEPTIONALLY
UNIDEOLOGICALLY UNIDIOMATICALLY UNOBJECTIONABLE UNOBJECTIONABLY
UNPATRIOTICALLY UNPHILOSOPHICAL UNRECONCILIABLE UNSATISFACTIONS
UNSOCIABILITIES UNSOPHISTICATED VASCULARISATION VASCULARIZATION
VERACIOUSNESSES VICARIOUSNESSES VIVACIOUSNESSES VORACIOUSNESSES
VOYEURISTICALLY WATERCOLOURISTS