Breadcrumb Home > Thesaurus > M Synonyms of mainline Find synonyms for: Verb 1. mainline, inject usage: inject into the vein; "She is mainlining heroin" WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved.Definition and meaning of mainline (Dictionary) TrendingHere are the facts and trivia that people are buzzing about. Hanukkah Origins of the Christmas Holiday Jewish Holidays, 2010-2030 (A.M. 5770-5791) Western Christian Holidays, 2010-2030 Krampus: The Christmas Devil Kwanzaa ✖ Related Content Daily Word Quiz: anomie Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language