/ Thesaurus / L Synonyms of long underwear Find synonyms for: Noun1. long underwear, union suit, undergarment, unmentionableusage: an undergarment with shirt and drawers in one pieceWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: tenacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language