Breadcrumb Home > Thesaurus > I Synonyms of inefficacious Find synonyms for: Adjective 1. inefficacious (vs. efficacious), ineffective#1, uneffective#1, ineffectual usage: lacking the power to produce a desired effect; "laws that are inefficacious in stopping crime" WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved.Definition and meaning of inefficacious (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: jactation Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language