n.
Function: transitive verb
Inflected Form: -teed ; -tee · ing
Date: 1731
1 : to undertake to answer for the debt, default, or miscarriage of < guarantee a loan>
2 : to engage for the existence, permanence, or nature of : undertake to do or secure < guarantee the winning of three tricks>
3 : to give security to < guaranteed her against loss>
4 : to assert confidently <I guarantee you'll like it>