1.a written assurance that some product or service will be provided or will meet certain specifications
2.a pledge that something will happen or that something is true;
there is no guarantee that they are not lying
3.a collateral agreement to answer for the debt of another in case that person defaults
1.give surety or assume responsibility;
I vouch for the quality of my products
2.make certain of;
This nest egg will ensure a nice retirement for us
3.promise to do or accomplish;
guarantee to free the prisoners
4.stand behind and guarantee the quality, accuracy, or condition of;
The dealer warrants all the cars he sells