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]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "uncouple":
   abrupt, abstract, alienate, cast off, cast out, cut adrift,
   cut off, cut out, delete, depart, disarticulate, disconnect,
   disengage, disjoin, disjoint, dissociate, disunite, divide,
   divorce, eject, estrange, expel, isolate, leave, part, pull away,
   pull back, pull out, segregate, separate, sequester, set apart,
   set aside, shut off, split, stand aloof, stand apart, stand aside,
   step aside, subtract, throw off, throw out, unyoke, withdraw