There are 547 twelve-letter words containing A, C, G, I and S, https://www.bestwordlist.com/c/a/5/12letterwordswithacgis.htm
ACAROLOGISTS ACCESSIONING ACROMEGALICS ACROMEGALIES AEROBICISING
AGARICACEOUS AGNOSTICISMS AGORAPHOBICS AGRICULTURES AGRIPRODUCTS
AGROSTOLOGIC ALCOHOLISING ALGOLAGNIACS ANASTIGMATIC ANGIOCARPOUS
ANGIOSARCOMA ANGLOMANIACS ANTAGONISTIC ARCHEOLOGIES ARCHEOLOGIST
ARCHIPELAGOS ARGILLACEOUS ASCERTAINING ASEPTICISING ASEPTICIZING
ASSURGENCIES ASTACOLOGIES ASTACOLOGIST ASTRINGENCES ASTROLOGICAL
AUSCULTATING AUTECOLOGIES BACKCROSSING BACKFILLINGS BACKFITTINGS
BACKPACKINGS BACKSHISHING BACKSLAPPING BACKSLIDINGS BACKSPEERING
BACKSPEIRING BACKSTABBING BACKSTALLING BACKSTAMPING BACKSTARTING
BACKSTOPPING BACKSTRAIGHT BACKSTROKING BAREBACKINGS BELLYACHINGS
BENIGNANCIES BESCATTERING BIOMAGNETICS BLACKLISTING BLACKWASHING
BLOGJACKINGS BLUEJACKINGS BRACHYLOGIES BRAGGADOCIOS BRICKLAYINGS
BRICKMAKINGS BROADCASTING BUSHWHACKING CABLECASTING CACOGRAPHIES
CAENOGENESIS CAINOGENESES CAINOGENESIS CALENDERINGS CALIGINOSITY
CALLIBOGUSES CALLIGRAMMES CANDLELIGHTS CAPARISONING CAPITALISING
CARAMELISING CARAVANNINGS CARDIOGRAPHS CARDIOLOGIES CARDIOLOGIST
CARDSHARPING CARPHOLOGIES CARPOLOGISTS CARRAGEENINS CARRIAGEWAYS
CASHMOBBINGS CASTIGATIONS CATABOLISING CATALOGISING CATALOGUISED
CATALOGUISES CATALOGUISTS CATALOGUIZES CATECHISINGS CATECHIZINGS
CATEGORISING CENTIGRAMMES CENTIMORGANS CENTRALISING CENTRIFUGALS
CEPHALALGIAS CEPHALALGICS CERARGYRITES CEROGRAPHIES CEROGRAPHIST
CHANDLERINGS CHANNELISING CHAPTALISING CHASMOGAMIES CHASTENINGLY
CHAUFFEUSING CHEESEPARING CHIKUNGUNYAS CHIMICHANGAS CINEMATISING
CIRCULATINGS CLADOGENESIS CLASSICISING CLASSICIZING CLEISTOGAMIC
CLIFFHANGERS CLISTOGAMIES CLOISONNAGES COAGULATIONS COASTEERINGS
COCKSWAINING COGNOMINATES COLLEGIALISM COLLEGIANERS COLLIGATIONS
COLOGARITHMS COLORCASTING COLORWASHING COMMEASURING COMPAGINATES
COMPENSATING COMPLAININGS CONCUBINAGES CONDENSATING CONFIGURATES
CONFISCATING CONGELATIONS CONJUGATINGS CONJUGATIONS CONSECRATING
CONSIGNATION CONSIGNATORY CONSOCIATING CONSTIPATING CONSTRAINING
CONSUMMATING CONTAGIONIST CONTAGIOUSLY CONVALESCING CONVERSATING
COPROPHAGIES COPROPHAGIST COPYREADINGS CORDIALISING CORRUGATIONS
COSMOGONICAL COSMOGRAPHIC COSMOLOGICAL CRAGGINESSES CRAMPONNINGS
CRANIOLOGIES CRANIOLOGIST CROSSBANDING CROSSBARRING CRYOSURGICAL
CRYPTOGAMIES CRYPTOGAMIST CRYSTALISING CRYSTALIZING CYANOGENESIS
CYCLOPLEGIAS DAMASCEENING DAMASCENINGS DECIMALISING DECREASINGLY
DEGENERACIES DELOCALISING DEMOGRAPHICS DESCRAMBLING DEVOCALISING
DIAGNOSTICAL DISACCORDING DISADVANCING DISAFFECTING DISANCHORING
DISAVAUNCING DISAVOUCHING DISBRANCHING DISCANDERING DISCANDYINGS
DISCOGRAPHER DISCOGRAPHIC DISCOURAGERS DISCOURAGING DISCULPATING
DISSOCIATING ECHOGRAPHIES EGOISTICALLY ELASTICATING ELASTICISING
ELASTICIZING EMASCULATING ENCOMPASSING ENCOURAGINGS EPISCOPATING
ESCAPOLOGIES ESCAPOLOGIST ESCHATOLOGIC EULOGISTICAL EVANGELICALS
EVANGELICISM EVANGELISTIC EVISCERATING EXACTINGNESS EXCOGITATORS
FACSIMILEING FANATICISING FIRESCAPINGS FLASHBACKING FORECASTINGS
FORESLACKING FRICASSEEING GALACTOSEMIA GALACTOSEMIC GALACTOSIDES
GALLINACEANS GALLINACEOUS GALLSICKNESS GALRAVITCHES GANCICLOVIRS
GASIFICATION GASOMETRICAL GASTROCNEMII GASTRONOMICS GASTROSCOPIC
GASTROTRICHS GATECRASHING GEANTICLINES GEMEINSCHAFT GENERATRICES
GENOCIDAIRES GEOGNOSTICAL GEOLOCATIONS GEOMECHANICS GEOSTRATEGIC
GEOSYNCLINAL GERANIACEOUS GESTICULATED GESTICULATES GESTICULATOR
GIGANTICIDES GIGANTICNESS GILRAVITCHES GLACIOLOGIES GLACIOLOGIST
GLOSSEMATICS GLUCOKINASES GLUCOSAMINES GLUCOSIDASES GLYCERINATES
GLYCOSIDASES GOALKICKINGS GRACIOSITIES GRACIOUSNESS GRADUALISTIC
GRAMINACEOUS GRAMMATICISE GRAMMATICISM GRANOLITHICS GRAPHICACIES
GRASSCYCLING GRASSFINCHES GRECIANISING GREENBACKISM GRIDDLECAKES
GYMNASIARCHS GYNECOMASTIA HAGIOCRACIES HAIRCUTTINGS HAMSHACKLING
HELICOGRAPHS HIGHJACKINGS HISTOLOGICAL HORSERACINGS HYGROCHASIES
HYGROCHASTIC HYPERALGESIC HYPSOGRAPHIC IMMIGRANCIES INCANDESCING
INCOGNISABLE INCOGNISANCE INCRASSATING INCREASINGLY INELEGANCIES
INFOGRAPHICS INGRAVESCENT INOSCULATING INTERCHANGES INTERFACINGS
INTERSPACING ISOANTIGENIC ISOMAGNETICS KICKSTARTING KNEECAPPINGS
LANDSCAPINGS LATCHSTRINGS LEGITIMACIES LEXICALISING LIMACOLOGIES
LIMACOLOGIST LINEBACKINGS LINECASTINGS LINGUISTICAL LOGANIACEOUS
LOGICALITIES LOGISTICALLY LOGISTICIANS LOGOMACHISTS MACADAMISING
MAGISTRACIES MAGNETICIANS MALACOLOGIES MALACOLOGIST MALIGNANCIES
MARCONIGRAMS MATCHMAKINGS MEATPACKINGS MEDICALISING MERCHANTINGS
METATUNGSTIC MICROGAMETES MICROMANAGES MICROPHAGOUS MINICABBINGS
MISBALANCING MISCARRIAGES MISCATALOGED MISCATALOGUE MISCEGENATED
MISCEGENATES MISCEGENATOR MISCHALLENGE MISEDUCATING MISGUIDANCES
MISPACKAGING MONARCHISING MONOGAMISTIC MUCILAGINOUS MUSEOLOGICAL
MUSICALISING MUSICALIZING MYCOPHAGISTS MYSTAGOGICAL NEGATIVISTIC
NEWSAGENCIES NEWSCASTINGS NIGHTCLASSES NIGROMANCIES NOCTIVAGANTS
NONSTRATEGIC NOSTOLOGICAL NUCLEARISING OCEANOLOGIES OCEANOLOGIST
OCTOGENARIES OLIGOCHAETES OPPUGNANCIES ORGANICISTIC ORGANICITIES
ORGASMICALLY ORGASTICALLY OSCILLOGRAMS OSCILLOGRAPH OSTEOLOGICAL
OUTSCREAMING OVERCASTINGS OVERCOATINGS PACESETTINGS PACKINGHOUSE
PANICMONGERS PARACHUTINGS PARALOGISTIC PARASCENDING PARATUNGSTIC
PASSACAGLIAS PEACEMAKINGS PESTOLOGICAL PHAGOCYTISED PHAGOCYTISES
PHAGOCYTISMS PHAGOCYTIZES PHAGOCYTOSIS PHAGOMANIACS PHRASEOLOGIC
PLAGIARISTIC PLAGIOCLASES PLASTICISING PLASTICIZING POSTORGASMIC
POSTSURGICAL PRAGMATICISM PRAGMATICIST PRAGMATISTIC PRECOGNISANT
PREDECEASING PREDISCHARGE PROFLIGACIES PUGILISTICAL PUGNACIOUSLY
QUACKSALVING QUINDECAGONS RACEWALKINGS RADICALISING RANSHACKLING
RECANALISING RECOGNISABLE RECOGNISABLY RECOGNISANCE REESCALATING
REFINANCINGS REGENERACIES REINCREASING REPUGNANCIES REPURCHASING
ROPEDANCINGS ROUGHCASTING RUSTICATINGS SACCHARISING SACCHARIZING
SACRAMENTING SACRILEGIOUS SACRILEGISTS SAFECRACKING SALICYLATING
SANCTIFYINGS SANCTIONINGS SATISFICINGS SCAFFOLDINGS SCAMBAITINGS
SCANDALISING SCANDALIZING SCAPEGOATING SCAPEGOATISM SCARIFYINGLY
SCATOLOGICAL SCATOLOGISTS SCATOPHAGIES SCATTERINGLY SCATTERLINGS
SCAVENGERIES SCAVENGERING SCENOGRAPHIC SCHEMATISING SCHEMATIZING
SCINTIGRAPHY SCRAMBLINGLY SCRAPBOOKING SCRATCHINGLY SCRIMSHAWING
SEARCHLIGHTS SECRETAGOGIC SECULARISING SECULARIZING SEMIOLOGICAL
SHELLACKINGS SIDETRACKING SIGNIFICANCE SIGNIFICANCY SIGNIFICANTS
SIGNIFICATES SIGNIFICATOR SIMULCASTING SINGLETRACKS SLACKLININGS
SOCIALISINGS SOCIALIZINGS SOCIOLOGICAL SPACEFARINGS SPACEFLIGHTS
SPACEWALKING SPAGYRICALLY SPECIALISING SPECIALIZING SPECIALOGUES
SPEECHMAKING SPHACELATING SPHRAGISTICS SPIFLICATING SPIROGRAPHIC
STAIRCASINGS STANCHELLING STANCHIONING STARFUCKINGS STENOGRAPHIC
STEPDANCINGS STERCORATING STOCKTAKINGS STYLOGRAPHIC SUBGLACIALLY
SUBMICROGRAM SUBSTRACTING SUFFOCATINGS SUGARCOATING SUPERGLACIAL
SUPERORGANIC SUPPLICATING SURFCASTINGS SYMBOLOGICAL SYNERGICALLY
TERMAGANCIES TOWNSCAPINGS TRACKLAYINGS TRAFFICKINGS TRAGICALNESS
TRANSCENDING TRANSCRIBING TRANSFECTING TSUNAMIGENIC TYPECASTINGS
UNCANONISING UNCARINGNESS UNCOALESCING UNDISCHARGED UNGRACIOUSLY
UNGUICULATES UNSCRAMBLING VAGINICOLOUS VESICULATING VICTUALLAGES
VOUCHSAFINGS WAINSCOTINGS WAINSCOTTING WAISTCOATING WALKINGSTICK
WARCHALKINGS WATCHMAKINGS WATCHSPRINGS WILDCATTINGS WISECRACKING
WITCHGRASSES WOODCARVINGS