Undersign

(v. t.) To write one's name at the foot or end of, as a letter or any legal instrument.

Thesaurus Entries

OK, accept, accredit, affirm, amen, approve, assure, attest, authenticate, authorize, autograph, back, be sponsor for, bond, certify, confirm, cosign, countersecure, countersign, endorse, ensure, give permission, give the go-ahead, give the imprimatur, give thumbs up, guarantee, guaranty, initial, insure, notarize, pass, pass on, pass upon, permit, ratify, rubber stamp, sanction, say amen to, seal, second, secure, sign, sign and seal, sign for, sponsor, stand behind, stand up for, subscribe to, support, swear and affirm, swear to, underwrite, validate, visa, vise, warrant