Mammoth Uncensored Word List:
23 words that are 20 letters long beginning with i in the mammoth uncensored word list.

immunocytochemically immunohistochemistry immunoprecipitations inappreciativenesses incommensurabilities incomprehensibleness inconsequentialities inconsiderablenesses indestructiblenesses indiscriminatenesses indistinguishability institutionalisation institutionalization intellectualizations interchangeabilities interconnectednesses internationalisation internationalization interstratifications irreconcilablenesses irreproachablenesses isopropylcyclohexane isopropylcyclohexene