Source : Webster's Revised Unabridged Dictionary (1913)

Unbolt \Un*bolt"\, v. t. [1st pref. un- + bolt.]
   To remove a bolt from; to unfasten; to unbar; to open. ``He
   shall unbolt the gates.'' --Shak.

Unbolt \Un*bolt"\, v. i.
   To explain or unfold a matter; to make a revelation. [Obs.]
   ``I will unbolt to you.'' --Shak.

Source : WordNet®

unbolt
     v : undo the bolt of; "unbolt the door" [ant: {bolt}]