/ Thesaurus / J Synonyms of junk mail Find synonyms for: Noun1. junk mail, third-class mail, third classusage: third-class mail consisting of advertising and often addressed to `resident' or `occupant'WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: coincidence Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language