The Collaborative International Dictionary of English v.0.48:

Dwindle \Dwin"dle\, v. i. [imp. & p. p. Dwindled; p. pr. & vb.
   n. Dwindling.] [From OE. dwinen to languish, waste away,
   AS. dw[imac]nan; akin to LG. dwinen, D. dwijnen to vanish,
   Icel. dv[imac]na to cease, dwindle, Sw. tvina; of uncertain
   origin. The suffix -le, preceded by d excrescent after n, is
   added to the root with a diminutive force.]
   To diminish; to become less; to shrink; to waste or consume
   away; to become degenerate; to fall away.
   [1913 Webster]

         Weary sennights nine times nine
         Shall he dwindle, peak and pine.         --Shak.
   [1913 Webster]

         Religious societies, though begun with excellent
         intentions,
         are said to have dwindled into factious clubs. --Swift.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

dwindling \dwindling\ adj.
   gradually decreasing until little remains.

   Syn: tapering, tapering off.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

dwindling \dwindling\ n.
   the act or process of becoming gradually less until little
   remains; as, there is no greater sadness that the dwindling
   away of a family.

   Syn: dwindling away.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

dwindling
    adj 1: gradually decreasing until little remains [syn:
           dwindling, tapering, tapering off]
    n 1: a becoming gradually less; "there is no greater sadness
         that the dwindling away of a family" [syn: dwindling,
         dwindling away]

Moby Thesaurus II by Grady Ward, 1.0:

111 Moby Thesaurus words for "dwindling":
   at rest, calm, catabasis, cloistered, collapse, coming apart,
   contractive, cool, cracking, crash, crumbling, decadent,
   deceleration, declension, decline, decline and fall, declining,
   decreasing, decrescendo, decrescent, degenerate, deliquescent,
   deteriorating, diminishing, diminuendo, disintegrating, dive,
   downtrend, downturn, draining, drooping, drop, dying, ebb, ebbing,
   effete, even-tenored, fading, failing, fall, falling, flagging,
   fragmenting, going to pieces, halcyon, hushed, impassive, isolated,
   languishing, lapse, lessening, marcescent, moldering, on the wane,
   pacific, peaceable, peaceful, pining, placid, plunge, quiescent,
   quiet, receding, reductive, regressive, remission, reposeful,
   reposing, restful, resting, retiring, retreat, retreating,
   retrograde, retrogressive, secluded, sequestered, sequestrated,
   sheltered, shrinking, shriveling, sinking, sliding, slipping,
   slowdown, slump, slumping, smooth, still, still as death, stillish,
   stilly, stoic, stolid, subsidence, subsiding, tabetic, tranquil,
   unagitated, undisturbed, unmoved, unperturbed, unruffled,
   unstirring, untroubled, wane, waning, wasting, wilting, withering,
   worsening