/ Thesaurus / F Synonyms of forth river Find synonyms for: Noun1. Forth, Forth Riverusage: a river in southern Scotland that flows eastward to the Firth of ForthWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: tenacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language