The Collaborative International Dictionary of English v.0.48:

Squander \Squan"der\ (skw[o^]n"d[~e]r), v. t. [imp. & p. p.
   Squandered (-d[~e]rd); p. pr. & vb. n. Squandering.] [Cf.
   Scot. squatter to splash water about, to scatter, to
   squander, Prov. E. swatter, Dan. sqvatte, Sw. sqv[aum]tta to
   squirt, sqv[aum]ttra to squander, Icel. skvetta to squirt
   out, to throw out water.]
   1. To scatter; to disperse. [Obs.]
      [1913 Webster]

            Our squandered troops he rallies.     --Dryden.
      [1913 Webster]

   2. To spend lavishly or profusely; to spend prodigally or
      wastefully; to use without economy or judgment; to
      dissipate; as, to squander an estate.
      [1913 Webster]

            The crime of squandering health is equal to the
            folly.                                --Rambler.
      [1913 Webster]

   Syn: To spend; expend; waste; scatter; dissipate.
        [1913 Webster]

WordNet (r) 3.0 (2006):

squandered
    adj 1: not used to good advantage; "squandered money cannot be
           replaced"; "a wasted effort" [syn: squandered,
           wasted]

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "squandered":
   ablated, by the board, consumed, depleted, dissipated,
   down the drain, eroded, expended, forfeit, forfeited, gone,
   gone to waste, irretrievable, long-lost, lost, lost to, misspent,
   out the window, run to seed, shrunken, spent, used, used up,
   wasted, worn away