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]