The Collaborative International Dictionary of English v.0.48:

Unlimber \Unlimber\
   See limber.

The Collaborative International Dictionary of English v.0.48:

Unlimber \Un*lim"ber\, v. t. [1st pref. un- + limber.] (Mil.)
   To detach the limber from; as, to unlimber a gun.
   [1913 Webster]