There are multiple definitions - click on the translation that matches your context.

afiançar

verbo

full

guarantee

verb

Definitions of guarantee

to make a formal promise that something will happen

We cannot guarantee the amount of work we would be able to give you.

to guarantee a debt to make a formal promise to accept the responsibility for someone's debt if that person cannot to pay it

Banks will not guarantee payments made by cheque over a certain amount.