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.
      [1913 Webster]

            The use of the elastic switch to fillip small
            missiles with.                        --Tylor.
      [1913 Webster]

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]

Moby Thesaurus II by Grady Ward, 1.0:

76 Moby Thesaurus words for "fillip":
   animate, bait, beak, bonus, bribe, brush, bunt, carrot, chuck, dab,
   decoration, encouragement, enliven, exhilarate, extra,
   extra added attraction, extra dash, filigree, filling, flick, flip,
   flirt, flourish, frill, galvanize, graze, incentive, incitement,
   inducement, infuse life into, interest, invigorate, invitation,
   jazz up, lagniappe, lure, ornament, padding, pat, payment, peck,
   percentage, persuasive, pick, pick up, pique, premium, profit,
   provocation, provoke, quicken, rap, renew, resuscitate, revive,
   reward, sharpen, snap, something extra, stimulate, stimulation,
   stimulative, stimulus, stuffing, superaddition, sweetener,
   sweetening, tap, tickle, tip, touch, trimming, twist, whet, whisk,
   wrinkle