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):

wasteful
    adj 1: inefficient in use of time and effort and materials; "a
           clumsy and wasteful process"; "wasteful duplication of
           effort"; "uneconomical ebb and flow of power" [syn:
           uneconomical, wasteful]
    2: tending to squander and waste [ant: thrifty]
    3: laying waste; "when wasteful war shall statues overturn"-
       Shakespeare

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "wasteful":
   baneful, calamitous, cataclysmal, cataclysmic, catastrophic,
   consuming, consumptive, deadly, demolishing, demolitionary,
   depredatory, desolating, destroying, destructive, devastating,
   disastrous, dissipative, doomful, easy come, easy go, extravagant,
   fatal, fateful, fratricidal, incontinent, intemperate, internecine,
   lavish, nihilist, nihilistic, overgenerous, overlavish,
   overliberal, penny-wise and pound-foolish, pound-foolish, prodigal,
   profligate, profuse, ravaging, ruining, ruinous, self-destructive,
   spendthrift, subversionary, subversive, suicidal, vandalic,
   vandalish, vandalistic, wasting, withering