guarantee

1 to assume responsibility for the satisfactory quality or performance of the shop will guarantee all work done on the car for 30 days Synonyms warrant, guarantyRelated Words attest, authenticate, avouch, certify, testify (to), vouch (for), witness; assure, bond, contract, covenant; pledge, plight, stipulate, swear, undertake, vow; adhere, assert, aver, avow, declare, insist; insure

2 to make sure, certain, or safe I can guarantee that you'll feel better after using my product for 30 days Synonyms assure, cinch, ensure, guaranty, ice, insure, secureRelated Words attest, certify, vouch, warrant, witness; pledge, promise, swearNear Antonyms enfeeble, undermine, weaken

3 to state clearly and strongly I guarantee that this movie is better than the last one in the series Synonyms affirm, aver, avouch, avow, declare, assert, lay down, professRelated Words advance, advertise, boost, plug, promote, publicize; announce, blaze, call, proclaim, pronounce, say; accent, accentuate, emphasize, stress, underline, underscore; advocate, champion, defend, espouse, support, uphold; assure, convince, persuade; explain, justify, rationalize; reaffirm, reassertNear Antonyms minimize, understate; disregard, ignore, neglect, overlook