The Collaborative International Dictionary of English v.0.48:

Wasteful \Waste"ful\, a.
   1. Full of waste; destructive to property; ruinous; as,
      wasteful practices or negligence; wasteful expenses.
      [1913 Webster]

   2. Expending, or tending to expend, property, or that which
      is valuable, in a needless or useless manner; lavish;
      prodigal; as, a wasteful person; a wasteful disposition.
      [1913 Webster]

   3. Waste; desolate; unoccupied; untilled. [Obs.]
      [1913 Webster]

            In wilderness and wasteful desert strayed.
                                                  --Spenser.
      [1913 Webster]

   Syn: Lavish; profuse; prodigal; extravagant.
        [1913 Webster] -- Waste"ful*ly, adv. --
        Waste"ful*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

wastefulness
    n 1: the trait of wasting resources; "a life characterized by
         thriftlessness and waste"; "the wastefulness of missed
         opportunities" [syn: thriftlessness, waste,
         wastefulness]
    2: useless or profitless activity; using or expending or
       consuming thoughtlessly or carelessly; "if the effort brings
       no compensating gain it is a waste"; "mindless dissipation of
       natural resources" [syn: waste, wastefulness,
       dissipation]