1. a promise or assurance that something will be done or will happen
2. a written agreement that a company will repair or replace a product if it breaks within a certain time period

1. to promise that something will happen or be done
2. to provide a written promise to repair or replace a product

Examples

• The company offers a money-back guarantee on all products.
• There's no guarantee that the weather will be good tomorrow.
• The warranty guarantees free repairs for two years.
• I can guarantee you'll love this restaurant.
• The manufacturer guarantees this appliance for five years.
• Success is never a guarantee in business.
• Can you guarantee delivery by Friday?