/ Thesaurus / P Synonyms of pillar box Find synonyms for: Noun1. pillar box, postbox, mailbox, letter boxusage: a red pillar-shaped letter boxWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: tactful Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language