COSIGNING is a playable word

cosign Scrabble® Dictionary

verb
cosigned, cosigning, cosigns
to sign jointly
90 Playable Words can be made from "COSIGNING"
   2-Letter Words (10 found)
   3-Letter Words (21 found)
   7-Letter Words (7 found)
   8-Letter Words (1 found)
   9-Letter Words (2 found)