/ Thesaurus / T Synonyms of tighten up Find synonyms for: Verb1. stiffen, tighten, tighten up, constrain, restrict, restrain, trammel, limit, bound, confine, throttleusage: restrict; "Tighten the rules"; "stiffen the regulations"WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: opulent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language