endorse

Synonyms: accredit advocate affirm approve attest authenticate back back up bless boost certify champion commend confirm countenance defend favor give a boost to give green light give one’s word give the go-ahead give the nod go along with go to bat for go with guarantee lend one’s name to okay praise push ratify recommend rubber-stamp sanction second stand behind stand up for stump for subscribe to sustain underwrite uphold vouch for warrant witness

Antonyms: censure disapprove oppose protest reject repel unauthorize

Synonyms: add one’s name to authenticate autograph cosign notarize put john hancock on put signature on rubber-stamp say amen to sign sign off on sign on dotted line subscribe superscribe undersign underwrite