[koh-sahyn, koh-sahyn]

verb (used with or without object)

to sign as a cosigner.

Origin of cosign Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Word Origin and History for cosign

also co-sign, by 1944, from co- + sign (v.). Related: Cosigned; cosigning.

Online Etymology Dictionary, © 2010 Douglas Harper