1 guaranty, warranty, assurance, pledge, bond, obligation, promise; word (of honour), oath, undertaking:
The guarantee expires one month from the sell-by date. Have I your guarantee that this battery will last a year?
2 guaranty, warranty, assure, ensure, pledge, promise, undertake, stand behind, vouch for, certify, make sure or certain, swear to, attest to:
The manufacturer guarantees every car for three years or 50,000 miles.