NOUN (1)

1. a gradual decrease in magnitude or extent;
- Example: "the waning of his enthusiasm was obvious"
- Example: "the waxing and waning of the moon"


ADJECTIVE (1)

1. (of the Moon) pertaining to the period during which the visible surface of the moon decreases;
- Example: "after full moon comes the waning moon"

The Collaborative International Dictionary of English v.0.48:

Waning \Wan"ing\, n.
   The act or process of waning, or decreasing.
   [1913 Webster]

         This earthly moon, the Church, hath fulls and wanings,
         and sometimes her eclipses.              --Bp. Hall.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Wane \Wane\, v. i. [imp. & p. p. Waned; p. pr. & vb. n.
   Waning.] [OE. wanien, AS. wanian, wonian, from wan, won,
   deficient, wanting; akin to D. wan-, G. wahnsinn, insanity,
   OHG. wan, wana-, lacking, wan?n to lessen, Icel. vanr
   lacking, Goth. vans; cf. Gr. ? bereaved, Skr. ?na wanting,
   inferior. ????. Cf. Want lack, and Wanton.]
   [1913 Webster]
   1. To be diminished; to decrease; -- contrasted with wax,
      and especially applied to the illuminated part of the
      moon.
      [1913 Webster]

            Like the moon, aye wax ye and wane.
            Waning moons their settled periods keep. --Addison.
      [1913 Webster]

   2. To decline; to fail; to sink.
      [1913 Webster]

            You saw but sorrow in its waning form. --Dryden.
      [1913 Webster]

            Land and trade ever will wax and wane together.
                                                  --Sir J.
                                                  Child.
      [1913 Webster]

WordNet (r) 3.0 (2006):

waning
    adj 1: (of the Moon) pertaining to the period during which the
           visible surface of the moon decreases; "after full moon
           comes the waning moon" [ant: waxing]
    n 1: a gradual decrease in magnitude or extent; "the waning of
         his enthusiasm was obvious"; "the waxing and waning of the
         moon" [ant: waxing]

Moby Thesaurus II by Grady Ward, 1.0:

95 Moby Thesaurus words for "waning":
   aging, at rest, calm, cloistered, coming apart, contractive, cool,
   cracking, crumbling, decadent, declining, decreasing, decrescendo,
   decrescent, degenerate, deliquescent, deteriorating, diminishing,
   diminuendo, disintegrating, doting, draining, drooping, dwindling,
   dying, ebbing, effete, even-tenored, fading, failing, falling,
   flagging, fragmenting, getting on, going to pieces, growing old,
   halcyon, hushed, impassive, isolated, languishing, lessening,
   marcescent, moldering, on the wane, pacific, peaceable, peaceful,
   pining, placid, quiescent, quiet, receding, reductive, regressive,
   reposeful, reposing, restful, resting, retiring, retreating,
   retrograde, retrogressive, secluded, senescent, sequestered,
   sequestrated, sheltered, shrinking, shriveling, sinking, sliding,
   slipping, slumping, smooth, still, still as death, stillish,
   stilly, stoic, stolid, subsiding, tabetic, tranquil, unagitated,
   undisturbed, unmoved, unperturbed, unruffled, unstirring,
   untroubled, wasting, wilting, withering, worsening