/ Thesaurus / H Synonyms of hard and fast Find synonyms for: Adjective1. hard-and-fast, strict, invariable (vs. variable)usage: (of rules) stringently enforced; "hard-and-fast rules"WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: simian Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language