[sure.ty] n, pl -ties [ME surte, fr. MF surte, fr. L securitat-, securitas security, fr. securus] (14c) 1: the state of being sure: as a: sure knowledge: certainty b: confidence in manner or behavior: assurance
2. a: a formal engagement (as a pledge) given for the fulfillment of an undertaking: guarantee b: ground of confidence or security
3: one who has become legally liable for the debt, default, or failure in duty of another -- sure.ty.ship n