Guar″an‐ty, v. t. [imp. & p. p.Guarantied (?); p. pr. & vb. n.Guarantying.] [From Guaranty, n.] In law and common usage: To undertake or engage that another person shall perform (what he has stipulated); to undertake to be answerable for (the debt or default of another); to engage to answer for the performance of (some promise or duty by another) in case of a failure by the latter to perform; to undertake to secure (something) to another, as in the case of a contingency. See Guarantee, v. t.
☞ Guaranty agrees in form with warranty. Both guaranty and guarantee are well authorized by legal writers in the United States. The prevailing spelling, at least for the verb, is guarantee.