The Collaborative International Dictionary of English v.0.48:

Fillip \Fil"lip\ (f[i^]l"l[i^]p), v. t. [imp. & p. p.
   Filliped; p. pr. & vb. n. Filliping.] [For filp, flip.
   Cf. Flippant.]
   1. To strike with the nail of the finger, first placed
      against the ball of the thumb, and forced from that
      position with a sudden spring; to snap with the finger.
      "You fillip me o' the head." --Shak.
      [1913 Webster]

   2. To snap; to project quickly.
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            The use of the elastic switch to fillip small
            missiles with.                        --Tylor.
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The Collaborative International Dictionary of English v.0.48:

Fillip \Fil"lip\, n.
   1. A jerk of the finger forced suddenly from the thumb; a
      smart blow.
      [1913 Webster]

   2. Something serving to rouse or excite.
      [1913 Webster]

            I take a glass of grog for a filip.   --Dickens.
      [1913 Webster]

WordNet (r) 3.0 (2006):

fillip
    n 1: anything that tends to arouse; "his approval was an added
         fillip" [syn: bonus, fillip]