Source : Webster's Revised Unabridged Dictionary (1913)

Unclasp \Un*clasp"\, v. t. [1st pref. un- + clasp.]
   To loose the clasp of; to open, as something that is
   fastened, or as with, a clasp; as, to unclasp a book; to
   unclasp one's heart.

Source : WordNet®

unclasp
     v : release from a clasp; "She clasped and unclasped her hands"
         [ant: {clasp}, {clasp}]