a warrant, pledge, or formal assurance given as security that another's debt or obligation will be fulfilled.

something that is taken or presented as security.

the act of giving security.

a person who acts as a guarantor.

guarantee.

noun

pledge , attestation , certification , promise , guarantee , warrant , warranty , bond , contract , certificate , charter , testament , security , earnest , token , surety , assurance , covenant , engagement , plight , solemn word , vow , word , word of honor , backer , guarantor , underwriter

verb

certify , warrant