<p><strong>Noun:</strong></p><ul><li>a promise or assurance, especially one in writing, that something is of specified quality, content, benefit, etc., or that it will perform satisfactorily for a given length of time:<ul><li>a money-back guarantee.</li></ul></li><li>an assurance that another’s obligation will be fulfilled, or something presented as such security; guaranty.</li><li>something that assures a particular outcome or condition:<ul><li>Wealth is no guarantee of happiness.</li></ul></li><li>a person who gives a guarantee or guaranty; guarantor.</li><li>a person to whom a guarantee is made.</li></ul><p><strong>Verb (used with object):</strong></p><ul><li>guaranteed, guaranteeing<ul><li>to secure, as by giving or taking security:<ul><li>A credit card guarantees your reservation at the hotel.</li></ul></li><li>to make oneself answerable for (something) on behalf of someone else who is primarily responsible:<ul><li>to guarantee the fulfillment of a contract.</li></ul></li><li>to undertake to ensure for another, as rights or possessions:<ul><li>The Constitution guarantees freedom of religion.</li></ul></li><li>to serve as a warrant or guaranty for.</li><li>to undertake to protect or indemnify:<ul><li>to guarantee a person against loss.</li></ul></li><li>to undertake (to do something):<ul><li>I will guarantee to prove every word I stated.</li></ul></li><li>to promise (usually followed by a clause as object):<ul><li>I guarantee that I'll be there.</li></ul></li></ul></li></ul>