The Collaborative International Dictionary of English v.0.48:

Encumber \En*cum"ber\, v. t. [imp. & p. p. Encumbered; p. pr.
   & vb. n. Encumbering.] [F. encombrer; pref. en- (L. in) +
   OF. combrer to hinder. See Cumber, and cf. Incumber.]
   [Written also incumber.]
   1. To impede the motion or action of, as with a burden; to
      retard with something superfluous; to weigh down; to
      obstruct or embarrass; as, his movements were encumbered
      by his mantle; his mind is encumbered with useless
      learning.
      [1913 Webster]

            Not encumbered with any notable inconvenience.
                                                  --Hooker.
      [1913 Webster]

   2. To load with debts, or other legal claims; as, to encumber
      an estate with mortgages.

   Syn: To load; clog; oppress; overload; embarrass; perplex;
        hinder; retard; obstruct; check; block.
        [1913 Webster]

WordNet (r) 3.0 (2006):

encumbered
    adj 1: loaded to excess or impeded by a heavy load; "a summer
           resort...encumbered with great clapboard-and-stucco
           hotels"- A.J.Liebling; "a hiker encumbered with a heavy
           backpack"; "an encumbered estate" [ant: unencumbered]