Source : Webster's Revised Unabridged Dictionary (1913)

Wane \Wane\, v. t.
   To cause to decrease. [Obs.] --B. Jonson.

Wane \Wane\, n.
   1. The decrease of the illuminated part of the moon to the
      eye of a spectator.

   2. Decline; failure; diminution; decrease; declension.

            An age in which the church is in its wane. --South.

            Though the year be on the wane.       --Keble.

   3. An inequality in a board. [Prov. Eng.] --Halliwell.

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}.]
   1. To be diminished; to decrease; -- contrasted with {wax},
      and especially applied to the illuminated part of the
      moon.

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

   2. To decline; to fail; to sink.

            You saw but sorrow in its waning form. --Dryden.

            Land and trade ever will wax and wane together.
                                                  --Sir J.
                                                  Child.

Wane \Wane\, n. (Forestry)
   The natural curvature of a log or of the edge of a board
   sawed from a log.

Source : WordNet®

wane
     n : a gradual decline (in size or strength or power or number)
         [syn: {ebb}, {ebbing}]
     v 1: grow smaller; "Interest in the project waned" [syn: {decline},
           {go down}]
     2: become smaller; "Interest in his novels waned" [ant: {wax}]
     3: decrease in phase; "the moon is waning" [ant: {wax}]