The Collaborative International Dictionary of English v.0.48:

Incumbrance \In*cum"brance\, n. [See Encumbrance.] [Written
   also encumbrance.]
   [1913 Webster]
   1. A burdensome and troublesome load; anything that impedes
      motion or action, or renders it difficult or laborious;
      clog; impediment; hindrance; check. --Cowper.
      [1913 Webster]

   2. (Law) A burden or charge upon property; a claim or lien
      upon an estate, which may diminish its value.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Encumbrance \En*cum"brance\, n. [Cf. OF. encombrance. Cf.
   Incumbrance.]
   1. That which encumbers; a burden which impedes action, or
      renders it difficult and laborious; a clog; an impediment.
      See Incumbrance.
      [1913 Webster]

   2. (Law) Same as Incumbrance.

   Syn: Burden; clog; impediment; check; hindrance.
        [1913 Webster]

WordNet (r) 3.0 (2006):

encumbrance
    n 1: an onerous or difficult concern; "the burden of
         responsibility"; "that's a load off my mind" [syn:
         burden, load, encumbrance, incumbrance, onus]
    2: a charge against property (as a lien or mortgage) [syn:
       encumbrance, incumbrance]
    3: any obstruction that impedes or is burdensome [syn:
       hindrance, hinderance, hitch, preventive,
       preventative, encumbrance, incumbrance, interference]