The Collaborative International Dictionary of English v.0.48:

Palpitation \Pal`pi*ta"tion\, n. [L. palpitatio: cf. F.
   palpitation.]
   A rapid pulsation; a throbbing; esp., an abnormal, rapid
   beating of the heart as when excited by violent exertion,
   strong emotion, or by disease.
   [1913 Webster]

WordNet (r) 3.0 (2006):

palpitation
    n 1: a rapid and irregular heart beat
    2: a shaky motion; "the shaking of his fingers as he lit his
       pipe" [syn: shaking, shakiness, trembling, quiver,
       quivering, vibration, palpitation]

Moby Thesaurus II by Grady Ward, 1.0:

165 Moby Thesaurus words for "palpitation":
   agitation, angina, angina pectoris, aortic insufficiency,
   aortic stenosis, apoplectic stroke, apoplexy, arrhythmia,
   arteriosclerosis, atherosclerosis, atrial fibrillation,
   auricular fibrillation, barrage, beat, beating, beriberi heart,
   cardiac arrest, cardiac insufficiency, cardiac shock,
   cardiac stenosis, cardiac thrombosis, carditis, chills of fear,
   cold creeps, cold shivers, cold sweat, congenital heart disease,
   cor biloculare, cor juvenum, cor triatriatum, coronary,
   coronary insufficiency, coronary thrombosis, creeps, dance,
   diastolic hypertension, didder, disquiet, disquietude, dithers,
   drum, drum music, drumbeat, drumfire, drumming, encased heart,
   endocarditis, extrasystole, fatty heart, fear and trembling,
   fibroid heart, fidgetiness, fidgets, flap, flask-shaped heart,
   flicker, flit, flitter, flop, flutter, frosted heart, goose bumps,
   gooseflesh, hairy heart, heart attack, heart block,
   heart condition, heart disease, heart failure, heartbeat,
   heartquake, heartthrob, heaving, high blood pressure,
   horripilation, hypertension, hypertensive heart disease,
   inquietude, ischemic heart disease, jimjams, mitral insufficiency,
   mitral stenosis, myocardial infarction, myocardial insufficiency,
   myocarditis, myovascular insufficiency, nervousness, ox heart,
   panting, paradiddle, paralytic stroke, paroxysmal tachycardia,
   patter, pericarditis, perturbation, pile, pitapat, pitter-patter,
   pound, pounding, premature beat, pseudoaortic insufficiency,
   pulmonary insufficiency, pulmonary stenosis, pulsation, pulse,
   quaking, quaver, quavering, quiver, quiver of terror, quivering,
   rat-a-tat, rat-tat, rat-tat-tat, rataplan, rattattoo, restlessness,
   rheumatic heart disease, rhythm, roll, round heart, rub-a-dub,
   ruff, ruffle, sclerosis, shake, shakes, shaking, shiver, shivers,
   shudder, spatter, splutter, sputter, staccato, stony heart, stroke,
   sweat, tachycardia, tat-tat, tattoo, tempo, thrill of fear, throb,
   throbbing, thrombosis, thrum, thumping, tom-tom, tremble,
   trembling, tremor, trepidation, trepidity, tricuspid insufficiency,
   tricuspid stenosis, turtle heart, twitter, uneasiness, unrest,
   varicose veins, varix, ventricular fibrillation, waver