[count] 1 : a usually written promise: such as a : a promise that the quality of something (such as a product that is being sold) will be as good as expected ▪ The washer comes with a guarantee against major defects. ▪ The software comes with a money-back guarantee. [=a promise that the money you spend on a product will be returned if the product is not good enough] b : a promise that something is true or real ▪ They wanted a guarantee that the document was authentic.
2 : a promise that something will happen or be done ▪ They want the new contract to include a guarantee of job security. ▪ The U.S. Constitution includes guarantees against unreasonable searches. ▪ He cited the First Amendment guarantee of free speech.
3 : a thing that makes something sure to happen or exist —often used in negative constructions ▪ There is no guarantee that they will approve the contract. [=there is no way to be sure that they will approve it] ▪ There's no guarantee they'll get here on time. ▪ She took the job even though there was no guarantee of permanent employment.
4 : something valuable that the owner will allow to be taken if a promise is not kept or a loan is not paid back ▪ We used our house as a guarantee for the loan. [=we said that the bank could take our house if we did not pay back the loan]