guaranteeguaranteeguarantees1noun1a promise that something will happen: I want a guarantee that you will do the work today.2a written promise by a company that it will repair a thing you have bought, or give you a new one, if it goes wrong: a two-year guaranteeThe computer is still under guarantee.guaranteeguaranteeguaranteesguaranteedguaranteeing2verb (guarantees, guaranteeing, guaranteed)1to promise that something will be done or will happen: I can't guarantee that I will be able to help you, but I'll try.2to say that you will repair a thing that somebody buys, or give them a new one, if it goes wrong: The television is guaranteed for three years.