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]