What is the meaning of Guarantee?

Anything that assures a certain outcome.

A legal assurance of something, e.g. a security for the fulfillment of an obligation.

More specifically, a written declaration that a certain product will be fit for a purpose and work correctly; a warranty

The person to whom a guarantee is made.

A person who gives such a guarantee; a guarantor.

To give an assurance that something will be done right.

To assume or take responsibility for a debt or other obligation.

To make something certain.

Source: wiktionary.org