›to promise that something will happen or is true: guarantee sb sthEuropean Airlines guarantees its customers top-quality service.guarantee that sth is sthWe guarantee that our products are 100% safe.be guaranteed (to be) sthTheir bread is guaranteed free of preservatives.
›to make something sure to happen or to be true: Good design does not always guarantee success.guarantee thatHow can we guarantee that no one can access our intranet?
›COMMERCEif a company guarantees a product or service, it gives a written promise to return the customer's money or repair or exchange the product if there is a problem with it within a particular period: guarantee sth for sthWe guarantee all our work for six months.
›BANKINGto offer something valuable to someone with the agreement that they can keep it if you fail to pay a loan or do what you promise: If you guarantee the loan, you will lose the business if you default on payments.