Definition of "Guarantee" :
noun: a written assurance that some product or service will be provided or will meet certain specifications
noun: an unconditional commitment that something will happen or that something is true
"There is no guarantee that they are not lying."
noun: a collateral agreement to answer for the debt of another in case that person defaults
verb: promise to do or accomplish
"Guarantee to free the prisoners."
verb: give surety or assume responsibility
verb: make certain of
"Preparation will guarantee success!."
verb: stand behind and guarantee the quality, accuracy, or condition of