Mammoth Uncensored Word List:
26 words ending with st, 17 letters long

anaesthesiologist biostratigraphist congregationalist constitutionalist conversationalist counterstrategist deconstructionist ethnomusicologist hydrometallurgist immunopathologist lepidopterologist neurophysiologist neuropsychiatrist neuropsychologist neurotoxicologist nonanthropologist noncooperationist nonfundamentalist nontraditionalist orthopsychiatrist postimpressionist postmillennialist psychopathologist reconstructionist redistributionist transcendentalist