From The Collaborative International Dictionary of English v.0.48 [gcide]:
Unbend \Un*bend"\, v. i.
1. To cease to be bent; to become straight or relaxed.
[1913 Webster]
2. To relax in exertion, attention, severity, or the like;
hence, to indulge in mirth or amusement.
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Unbend \Un*bend"\ ([u^]n*b[e^]nd"), v. t. [imp. & p. p. Unbent
([u^]n*b[e^]nt"); p. pr. & vb. n. Unbending.] [1st pref.
un- + bend.]
1. To free from flexure; to make, or allow to become,
straight; to loosen; as, to unbend a bow.
[1913 Webster]
2. 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.
[1913 Webster]
You do unbend your noble strength. --Shak.
[1913 Webster]
3. (Naut.)
(a) To unfasten, as sails, from the spars or stays to
which they are attached for use.
(b) To cast loose or untie, as a rope.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
unbend
v 1: straighten up or out; make straight [syn: straighten,
unbend] [ant: bend, flex]
2: unfasten, as a sail, from a spar or a stay
3: free from flexure; "unbend a bow" [ant: bend, deform,
flex, turn, twist]
4: make less taut; "relax the tension on the rope" [syn:
relax, unbend]
5: become less tense, rest, or take one's ease; "He relaxed in
the hot tub"; "Let's all relax after a hard day's work" [syn:
relax, loosen up, unbend, unwind, decompress, {slow
down}] [ant: tense, tense up]
6: release from mental strain, tension, or formality; "unbend
the mind from absorbing too much information"