The Collaborative International Dictionary of English v.0.48:

Unmoor \Un*moor"\, v. t. [1st pref. un- + moor.] (Naut.)
   (a) To cause to ride with one anchor less than before, after
       having been moored by two or more anchors.
   (b) To loose from anchorage. See Moor, v. t.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Unmoor \Un*moor"\, v. i.
   To weigh anchor. --Sir W. Scott.
   [1913 Webster]