The Collaborative International Dictionary of English v.0.48:

Dissipation \Dis`si*pa"tion\ (d[i^]s`s[i^]*p[=a]"sh[u^]n), n.
   [L. dissipatio: cf. F. dissipation.]
   1. The act of dissipating or dispersing; a state of
      dispersion or separation; dispersion; waste.
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            Without loss or dissipation of the matter. --Bacon.
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            The famous dissipation of mankind.    --Sir M. Hale.
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   2. A dissolute course of life, in which health, money, etc.,
      are squandered in pursuit of pleasure; profuseness in
      vicious indulgence, as late hours, riotous living, etc.;
      dissoluteness.
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            To reclaim the spendthrift from his dissipation and
            extravagance.                         --P. Henry.
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   3. A trifle which wastes time or distracts attention.
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            Prevented from finishing them [the letters] a
            thousand avocations and dissipations. --Swift.
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   Dissipation of energy. Same as Degradation of energy,
      under Degradation.
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WordNet (r) 3.0 (2006):

dissipation
    n 1: breaking up and scattering by dispersion; "the dissipation
         of the mist"
    2: dissolute indulgence in sensual pleasure [syn: profligacy,
       dissipation, dissolution, licentiousness, looseness]
    3: 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]