PALPITATING
palpitant, palpitating
(adjective) having a slight and rapid trembling motion; “palpitant movements rather than violent eruptions”; “my palpitating heart”
Source: WordNet® 3.1
Verb
palpitating
present participle of palpitate
Source: Wiktionary
PALPITATE
Pal"pi*tate, v. i. [imp. & p. p. Palpitated; p. pr. & vb. n.
Palpitating().] Etym: [L. palpitare, palpitatum, v. intens. fr.
pappare. See Palpable.]
Definition: 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.
Source: Webster’s Unabridged Dictionary 1913 Edition