From The Collaborative International Dictionary of English v.0.48:
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.
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You do unbend your noble strength. --Shak.
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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]