The Collaborative International Dictionary of English v.0.48:

Lumbering \Lum"ber*ing\, n.
   The business of cutting or getting timber or logs from the
   forest for lumber. [U.S.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lumber \Lum"ber\, v. t. [imp. & p. p. Lumbered; p. pr. & vb.
   n. Lumbering.]
   1. To heap together in disorder. " Stuff lumbered together."
      --Rymer.
      [1913 Webster]

   2. To fill or encumber with lumber; as, to lumber up a room.
      [1913 Webster]

WordNet (r) 3.0 (2006):

lumbering
    adj 1: slow and laborious because of weight; "the heavy tread of
           tired troops"; "moved with a lumbering sag-bellied trot";
           "ponderous prehistoric beasts"; "a ponderous yawn" [syn:
           heavy, lumbering, ponderous]
    n 1: the trade of cutting or preparing or selling timber