Source : Webster's Revised Unabridged Dictionary (1913)

Undock \Un*dock"\, v. t. [1st pref. un- + dock.] (Naut.)
   To take out of dock; as, to undock a ship.

Source : WordNet®

undock
     v 1: move out of a dock; "We docked at noon" [ant: {dock}]
     2: take out of a dock; "undock the ship" [ant: {dock}]