COSIGN is a playable word

cosign Scrabble® Dictionary

verb
cosigned, cosigning, cosigns
to sign jointly
52 Playable Words can be made from "COSIGN"
   2-Letter Words (10 found)
   3-Letter Words (18 found)
   4-Letter Words (14 found)
   5-Letter Words (7 found)
   6-Letter Words (3 found)