Mammoth Uncensored Word List:
16 words ending with a, 18 letters long

aceruloplasminemia agammaglobulinemia arachibutyrophobia cholangiocarcinoma erythroprosopalgia hemangiopericytoma hyperbilirubinemia hyperglycorrhachia pheochromocytomata polychromatophilia pseudoparenchymata pteromerhanophobia rhabdomyosarcomata sesquipedalophobia sympathicoblastoma ultramicrobacteria