Breadcrumb Home > Thesaurus > P Synonyms of pony express Find synonyms for: Noun1. pony express, express, express mailusage: express mail carried by relays of riders on horseback; especially between Missouri and California around 1860WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. ✖ Related Content Daily Word Quiz: legerdemain Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language