From un- + brace.
unbrace (third-person singular simple present unbraces, present participle unbracing, simple past and past participle unbraced)
- (transitive) To undo, unfasten; to relax, loosen.
- 1590, Edmund Spenser, The Faerie Queene, II.iv:
- The knight emboyling in his haughtie hart, / Knit all his forces, and gan soone vnbrace / His grasping hold [...].