Synonyms and related words :
assure, attest, back, back up, be sponsor for, bond, certify, champion, confirm, countersecure, endorse, ensure, get behind, get in behind, guarantee, guaranty, insure, run interference for, second, secure, side with, sign, sign for, sponsor, stand back of, stand by, stand up for, stick by, stick up for, subscribe to, take sides with, undersign, underwrite, warrant