/ Dictionary / Index C cosign: Meaning and Definition of Find definitions for: co•sign Pronunciation: (kō'sīn", kō-sīn'), [key] — v.i., v.t. to sign as a cosigner. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: cosign (Thesaurus) Così fan tutte* cosignatory Related Content Daily Word Quiz: reclusive Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language