There are 599 twelve-letter words containing A, C, G, I and T, https://www.bestwordlist.com/c/a/5/12letterwordswithacgit.htm
ACAROLOGISTS ACCELERATING ACCENTUATING ACCUMULATING ADJUDICATING
AEROMAGNETIC AETIOLOGICAL AFFECTIONING AGAMOGENETIC AGNOSTICISMS
AGRAMMATICAL AGRICULTURAL AGRICULTURES AGRIPRODUCTS AGROSTOLOGIC
ANAGLYPTICAL ANAGRAMMATIC ANASTIGMATIC ANDROGENETIC ANNUNCIATING
ANTAGONISTIC ANTHOLOGICAL ANTIALLERGIC ANTICIPATING ANTICLOTTING
ANTIDOGMATIC ANTIGENICITY ANTILYNCHING ANTIMAGNETIC ANTIPOACHING
AORTOGRAPHIC APOGEOTROPIC APOLOGETICAL APOTHEGMATIC APPRECIATING
APPRENTICING ARCHEGONIATE ARCHEOLOGIST ARCHITECTING ARTICULATING
ASCERTAINING ASEPTICISING ASEPTICIZING ASTACOLOGIES ASTACOLOGIST
ASTRINGENCES ASTROLOGICAL ATHEOLOGICAL ATTRACTINGLY AUSCULTATING
AUTECOLOGIES BACKCHATTING BACKFITTINGS BACKLIGHTING BACKSTABBING
BACKSTALLING BACKSTAMPING BACKSTARTING BACKSTOPPING BACKSTRAIGHT
BACKSTROKING BACKTRACKING BACTERIOLOGY BANDICOOTING BATHYGRAPHIC
BATHYPELAGIC BATTOLOGICAL BESCATTERING BIOGENETICAL BIOMAGNETICS
BIRDWATCHING BLACKLISTING BLACKTOPPING BROADCASTING CABLECASTING
CACHINNATING CAENOGENETIC CAFFEINATING CAINOGENETIC CALIGINOSITY
CALUMNIATING CAMPHORATING CANDLELIGHTS CANTILLATING CAPACITATING
CAPITALISING CAPITALIZING CAPITULATING CARBURETTING CARDIOLOGIST
CARICATURING CARPENTERING CARPOLOGISTS CARTOGRAPHIC CARTOLOGICAL
CARTWHEELING CASTIGATIONS CATABOLISING CATABOLIZING CATALOGISING
CATALOGIZING CATALOGUISED CATALOGUISES CATALOGUISTS CATALOGUIZED
CATALOGUIZES CATECHISINGS CATECHIZINGS CATEGORIALLY CATEGORISING
CATEGORIZING CATERWAULING CENTIGRAMMES CENTIMORGANS CENTRALISING
CENTRALIZING CENTRIFUGALS CERARGYRITES CEROGRAPHIST CHAPTALISING
CHAPTALIZING CHARACTERING CHASTENINGLY CHITCHATTING CHLORIDATING
CHLORINATING CINEMATISING CINEMATIZING CIRCULATINGS CIRCUMGYRATE
CLADOGENETIC CLATTERINGLY CLEARCUTTING CLEISTOGAMIC CLIMATOLOGIC
CLISTOGAMIES COACERVATING COAGULATIONS COASTEERINGS COCAPTAINING
COGENERATION COGITATINGLY COGITATIVELY COGNOMINATED COGNOMINATES
COLLEGIALITY COLLEGIATELY COLLIGATIONS COLLIQUATING COLOGARITHMS
COLORCASTING COMMENTATING COMPAGINATED COMPAGINATES COMPENSATING
COMPLICATING COMPURGATION CONCILIATING CONDENSATING CONFIGURATED
CONFIGURATES CONFIGURATOR CONFISCATING CONGELATIONS CONGENIALITY
CONGENITALLY CONGLOBATING CONGLOBATION CONGLUTINANT CONGLUTINATE
CONGREGATING CONGREGATION CONGREGATIVE CONJUGATINGS CONJUGATIONS
CONSECRATING CONSIGNATION CONSIGNATORY CONSOCIATING CONSTIPATING
CONSTRAINING CONSUMMATING CONTAGIONIST CONTAGIOUSLY CONTIGNATION
CONTRAVENING CONVERSATING COORDINATING COPARTNERING COPROPHAGIST
CORRUGATIONS COTANGENTIAL COUNTERIMAGE CRANIOLOGIST CRENELLATING
CRYPTOGAMIAN CRYPTOGAMIES CRYPTOGAMIST CRYSTALISING CRYSTALIZING
CYANOGENETIC DACTYLIOLOGY DEACTIVATING DECAPITATING DECELERATING
DECOLORATING DEGLACIATION DENUNCIATING DEPRECIATING DERACINATING
DERMATOLOGIC DETOXICATING DETRACTINGLY DETRUNCATING DIABETOGENIC
DIAGEOTROPIC DIAGNOSTICAL DIAGRAMMATIC DIALECTOLOGY DIJUDICATING
DILACERATING DILUCIDATING DISAFFECTING DISCULPATING DISSOCIATING
DITTOGRAPHIC DIVARICATING DOGMATICALLY DOOMWATCHING ECHOLOCATING
EDULCORATING EFFECTUATING EGOCENTRICAL EGOISTICALLY ELASTICATING
ELASTICISING ELASTICIZING ELUCUBRATING EMANCIPATING EMASCULATING
ENCHANTINGLY ENCURTAINING ENTRANCINGLY EPEXEGETICAL EPIGRAMMATIC
EPISCOPATING EQUIVOCATING EROTOLOGICAL ESCAPOLOGIST ESCHATOLOGIC
ETHNOGRAPHIC ETHNOLOGICAL ETYMOLOGICAL EULOGISTICAL EVANGELISTIC
EVISCERATING EXACERBATING EXACTINGNESS EXCOGITATING EXCOGITATION
EXCOGITATIVE EXCOGITATORS EXCRUCIATING EXEGETICALLY EXTRALOGICAL
EXULCERATING FACEPLANTING FACILITATING FANATICISING FANATICIZING
FELICITATING FLOCCULATING FLOWCHARTING FORECASTINGS FORETEACHING
GALACTOSEMIA GALACTOSEMIC GALACTOSIDES GALRAVITCHED GALRAVITCHES
GAMETOPHORIC GAMETOPHYTIC GAMIFICATION GASIFICATION GASOMETRICAL
GASTROCNEMII GASTRONOMICS GASTROSCOPIC GASTROTRICHS GATECRASHING
GEANTICLINAL GEANTICLINES GEMEINSCHAFT GENERATRICES GENETHLIACAL
GENETHLIACON GENICULATELY GENICULATING GENICULATION GEOBOTANICAL
GEOCENTRICAL GEODETICALLY GEOGNOSTICAL GEOLOCATIONS GEOMETRICIAN
GEOPOLITICAL GEOSTRATEGIC GEOTECHNICAL GERIATRICIAN GESTICULATED
GESTICULATES GESTICULATOR GIGANTICALLY GIGANTICIDES GIGANTICNESS
GIGANTOMACHY GILRAVITCHED GILRAVITCHES GLACIOLOGIST GLOSSEMATICS
GLYCERINATED GLYCERINATES GONADOTROPIC GRACIOSITIES GRADUALISTIC
GRAMMATICISE GRAMMATICISM GRAMMATICIZE GRANOLITHICS GRANULOCYTIC
GYNECOCRATIC GYNECOMASTIA GYROMAGNETIC HAEMATOGENIC HAEMATOLOGIC
HAIRCUTTINGS HANDCRAFTING HECTOGRAPHIC HEPATICOLOGY HERETICATING
HISTOLOGICAL HYETOGRAPHIC HYGROCHASTIC ICHTHYOPHAGY ILLEGITIMACY
ILLOGICALITY INACTIVATING INCATENATING INCINERATING INCOGITATIVE
INCRASSATING INGRAVESCENT INOSCULATING INTERARCHING INTERCHANGED
INTERCHANGER INTERCHANGES INTERFACINGS INTERGLACIAL INTERSPACING
INTOXICATING IRRADICATING ISOANTIGENIC ISOMAGNETICS JACKLIGHTING
KAINOGENETIC KICKSTARTING LATCHSTRINGS LEGITIMACIES LIMACOLOGIST
LINECASTINGS LINGUISTICAL LITHOGRAPHIC LITHOLOGICAL LITURGICALLY
LOGICALITIES LOGISTICALLY LOGISTICIANS LOGOMACHISTS LONGICAUDATE
LYMPHANGITIC MAGISTRACIES MAGNETICALLY MAGNETICIANS MALACOLOGIST
MARTYROLOGIC MATCHMAKINGS MATCHMARKING MEATPACKINGS MERCHANTINGS
METAGALACTIC METALLOGENIC METATUNGSTIC METROLOGICAL MICROGAMETES
MICROGRANITE MICROGRAVITY MISCATALOGED MISCATALOGUE MISCEGENATED
MISCEGENATES MISCEGENATOR MISEDUCATING MONOGAMISTIC MUTAGENICITY
MYCOPHAGISTS MYSTAGOGICAL MYTHOLOGICAL NEGATIVISTIC NEWSCASTINGS
NIDIFICATING NIGHTCLASSES NOCTIVAGANTS NONANTIGENIC NONSTRATEGIC
NOSTOLOGICAL OBTRUNCATING OCEANOLOGIST OCTOGENARIAN OCTOGENARIES
OLIGOCHAETES ORGANICISTIC ORGANICITIES ORGANOLEPTIC ORGASTICALLY
ORTHOGNATHIC ORTHOGRAPHIC OSTEOLOGICAL OUTACHIEVING OUTBALANCING
OUTCAVILLING OUTCRAFTYING OUTLAUNCHING OUTPREACHING OUTSCREAMING
OVERCASTINGS OVERCATCHING OVERCOATINGS OVERMATCHING OVERREACTING
OVERTEACHING OVERWATCHING PACESETTINGS PACIFICATING PAEDOGENETIC
PALINGENETIC PANTOGRAPHIC PARACHUTINGS PARADIGMATIC PARALOGISTIC
PARAMAGNETIC PARATUNGSTIC PATCHWORKING PATHOGENETIC PATHOLOGICAL
PATROLOGICAL PERNOCTATING PESTOLOGICAL PETROGRAPHIC PETROLOGICAL
PHAGOCYTICAL PHAGOCYTISED PHAGOCYTISES PHAGOCYTISMS PHAGOCYTIZED
PHAGOCYTIZES PHAGOCYTOSIS PHAGOCYTOTIC PHLEGMATICAL PHOTOGRAPHIC
PHYTOGRAPHIC PHYTOLOGICAL PICTOGRAPHIC PLAGIARISTIC PLAGIOTROPIC
PLASTICISING PLASTICIZING POSTORGASMIC POSTSURGICAL PRAGMATICISM
PRAGMATICIST PRAGMATISTIC PRECOGNISANT PRECOGNIZANT PROGRAMMATIC
PUGILISTICAL PUNCTULATING PYROMAGNETIC QUITCLAIMING RACKETEERING
RACONTEURING REACTIVATING REALLOCATING RECATALOGING RECATEGORIZE
RECAUTIONING RECHARTERING RECOMPACTING RECONTACTING RECUPERATING
REDECORATING REDEDICATING REESCALATING REFRACTURING RETICULATING
REVICTUALING ROUGHCASTING RUSTICATINGS SACRAMENTING SACRILEGISTS
SALICYLATING SANCTIFYINGS SANCTIONINGS SATISFICINGS SCAMBAITINGS
SCAPEGOATING SCAPEGOATISM SCATOLOGICAL SCATOLOGISTS SCATOPHAGIES
SCATTERINGLY SCATTERLINGS SCHEMATISING SCHEMATIZING SCINTIGRAPHY
SCRATCHINGLY SEARCHLIGHTS SECRETAGOGIC SIDETRACKING SIGNIFICANTS
SIGNIFICATES SIGNIFICATOR SIMULCASTING SINGLETRACKS SPACEFLIGHTS
SPHACELATING SPHRAGISTICS SPIFLICATING STAIRCASINGS STANCHELLING
STANCHIONING STARFUCKINGS STENOGRAPHIC STEPDANCINGS STERCORATING
STOCKTAKINGS STYLOGRAPHIC SUBSTRACTING SUFFOCATINGS SUGARCOATING
SUPPLICATING SURFCASTINGS TABERNACLING TACHYGRAPHIC TAUTOLOGICAL
TELEOLOGICAL TELERGICALLY TERMAGANCIES THAUMATURGIC THEURGICALLY
THIGMOTACTIC THUMBTACKING TOWNSCAPINGS TRACKLAYINGS TRAFFICKINGS
TRAGICALNESS TRAGICOMICAL TRANSCENDING TRANSCRIBING TRANSFECTING
TRIBOLOGICAL TRICHOGYNIAL TRIFURCATING TRIGLYPHICAL TRIGRAMMATIC
TRIPLICATING TROPOLOGICAL TSUNAMIGENIC TYPECASTINGS UGLIFICATION
UNAPOLOGETIC UNCURTAINING UNDERCOATING UNGUICULATED UNGUICULATES
VATICINATING VESICULATING VICTUALLAGES VOCIFERATING WAINSCOTINGS
WAINSCOTTING WAISTCOATING WALKINGSTICK WATCHDOGGING WATCHMAKINGS
WATCHSPRINGS WILDCATTINGS WITCHGRASSES ZYGODACTYLIC