The Collaborative International Dictionary of English v.0.48:

Disengagement \Dis`en*gage"ment\, n. [Pref. dis- + engagement:
   cf. F. d['e]sengagement.]
   1. The act of disengaging or setting free, or the state of
      being disengaged.
      [1913 Webster]

            It is easy to render this disengagement of caloric
            and light evident to the senses.      --Transl. of
                                                  Lavoisier.
      [1913 Webster]

            A disengagement from earthly trammels. --Sir W.
                                                  Jones.
      [1913 Webster]

   2. Freedom from engrossing occupation; leisure.
      [1913 Webster]

            Disengagement is absolutely necessary to enjoyment.
                                                  --Bp. Butler.
      [1913 Webster]

WordNet (r) 3.0 (2006):

disengagement
    n 1: the act of releasing from an attachment or connection [syn:
         detachment, disengagement]
    2: to break off a military action with an enemy [syn:
       disengagement, fallback, pullout]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "disengagement":
   abstraction, alienation, breaking out, clearing, detachment,
   disarticulation, disassociation, disburdening, disconnectedness,
   disconnection, discontinuity, disembarrassment, disembroilment,
   disencumbrance, disentanglement, disinvolvement, disjointing,
   disjunction, dislocation, dislodgment, disunion, division, divorce,
   divorcement, extrication, fallback, freeing, incoherence,
   isolation, luxation, parting, partition, pullback, pullout,
   reculade, releasing, removal, retirement, retreat, segmentation,
   separation, separatism, subdivision, subtraction, uncluttering,
   unhampering, unknotting, unraveling, unscrambling, unsnarling,
   untangling, withdrawal, withdrawment, zoning