/ Dictionary / Index C cosigner: Meaning and Definition of Find definitions for: co•sign•er Pronunciation: (kō'sī"nur, kō-sī'-), [key] — n. a cosignatory. a joint signer of a negotiable instrument, esp. a promissory note. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: cosigner (Thesaurus) cosignatory Cosimo 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