(1):

(v. t.) To cast loose or untie, as a rope.

(2):

(v. t.) A remit from a strain or from exertion; to set at ease for a time; to relax; as, to unbend the mind from study or care.

(3):

(v. t.) To free from flexure; to make, or allow to become, straight; to loosen; as, to unbend a bow.

(4):

(v. i.) To relax in exertion, attention, severity, or the like; hence, to indulge in mirth or amusement.

(5):

(v. i.) To cease to be bent; to become straight or relaxed.

(6):

(v. t.) To unfasten, as sails, from the spars or stays to which they are attached for use.