Something that assures a particular outcome or condition: Lack of interest is a guarantee of failure.
A promise or assurance, especially one given in writing, that attests to the quality or durability of a product or service. A pledge that something will be performed in a specified manner.
A guarantor.
A guaranty.
To assume responsibility for the debt, default, or miscarriage of.
To assume responsibility for the quality or performance of: guarantee a product.
To undertake to do, accomplish, or ensure (something) for another: guaranteed to free the captives; guarantees freedom of speech.
To make certain: The rain guarantees a good crop this year.
To guaranty.
To furnish security for.
To express or declare with conviction: I guarantee that you'll like this book.