Source : Webster's Revised Unabridged Dictionary (1913)

Flicker \Flick"er\ (-[~e]r), v. i. [imp. & p. p. {Flickered}
   (-[~e]rd); p. pr. & vb. n. {Flickering}.] [OE. flikeren,
   flekeren, to flutter, AS. flicerian, flicorian, cf. D.
   flikkeren to sparkle. [root]84. Cf. Flacker.]
   1. To flutter; to flap the wings without flying.

            And flickering on her nest made short essays to
            sing.                                 --Dryden.

   2. To waver unsteadily, like a flame in a current of air, or
      when about to expire; as, the flickering light.

            The shadows flicker to fro.           --Tennyson.

Flicker \Flick"er\, n.
   1. The act of wavering or of fluttering; flucuation; sudden
      and brief increase of brightness; as, the last flicker of
      the dying flame.

   2. (Zo["o]l.) The golden-winged woodpecker ({Colaptes
      aurutus}); -- so called from its spring note. Called also
      {yellow-hammer}, {high-holder}, {pigeon woodpecker}, and
      {yucca}.

            The cackle of the flicker among the oaks.
                                                  --Thoureau.

Source : WordNet®

flicker
     n 1: a momentary flash of light [syn: {spark}, {glint}]
     2: North American woodpecker
     3: the act of moving back and forth [syn: {waver}, {flutter}]

flicker
     v 1: move back and forth very rapidly; "the candle flickered"
          [syn: {waver}, {flitter}, {flutter}, {quiver}]
     2: shine unsteadily; "The candle flickered" [syn: {flick}]
     3: flash intermittently; "The lights flicked on and off" [syn:
        {flick}]