Mammoth Uncensored Word List:
33 - 14 letter words starting with as

ascertainments aspiringnesses assassinations assaultiveness asseveratingly assimilability assimilatively assistantships associateships associationism associationist assortednesses assumabilities assumptiveness asthenospheres asthenospheric astigmatically astragalectomy astrapophobias astrapophobics astrobiologies astrobiologist astrochemistry astrocompasses astrogeologies astrogeologist astrologically astronavigator astronomically astrophysicist asymmetrically asymptotically asynchronously