/ Thesaurus / I Synonyms of impermissibly Find synonyms for: Adverb1. impermissiblyusage: not permissibly; "the radon level in the basement was impermissibly high"WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: penury Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language