The Collaborative International Dictionary of English v.0.48:

Uncouple \Un*cou"ple\, v. t. [1st pref. un- + couple.]
   To loose, as dogs, from their couples; also, to set loose; to
   disconnect; to disjoin; as, to uncouple railroad cars.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Uncouple \Un*cou"ple\, v. i.
   To roam at liberty. [Obs.] --Chaucer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

uncouple
    v 1: disconnect or separate; "uncouple the hounds" [syn:
         uncouple, decouple] [ant: couple, couple on,
         couple up]