The Collaborative International Dictionary of English v.0.48:

Palpitate \Pal"pi*tate\, v. i. [imp. & p. p. Palpitated; p.
   pr. & vb. n. Palpitating.] [L. palpitare, palpitatum, v.
   intens. fr. pappare. See Palpable.]
   To beat rapidly and more strongly than usual; to throb; to
   bound with emotion or exertion; to pulsate violently; to
   flutter; -- said specifically of the heart when its action is
   abnormal, as from excitement.
   [1913 Webster]

WordNet (r) 3.0 (2006):

palpitate
    v 1: cause to throb or beat rapidly; "Her violent feelings
         palpitated the young woman's heart"
    2: shake with fast, tremulous movements; "His nostrils
       palpitated" [syn: quiver, quake, palpitate]
    3: beat rapidly; "His heart palpitated" [syn: palpitate,
       flutter]

Moby Thesaurus II by Grady Ward, 1.0:

68 Moby Thesaurus words for "palpitate":
   beat, beat a ruffle, beat a tattoo, bicker, dance, drum, fidget,
   flap, flick, flicker, flip, flip out, flit, flitter, flop, flutter,
   freak out on, get high on, glow, go pitapat, gutter,
   have the fidgets, have the shakes, heave, jerk, pant, patter,
   pitter-patter, pound, pulsate, pulse, quake, quaver, quiver, roll,
   ruffle, shake, shiver, slat, sound a tattoo, splatter, splutter,
   sputter, squirm, swell, swell with emotion, thrill, thrill to,
   throb, thrum, thump, tick, ticktock, tingle,
   tingle with excitement, toss, toss and turn, tremble, tumble,
   turn on to, twist and turn, twitch, twitter, wave, waver, wiggle,
   wriggle, writhe