"palpitating" in the verb sense
1. palpitate
cause to throb or beat rapidly
"Her violent feelings palpitated the young woman's heart"
2. quiver, quake, palpitate
shake with fast, tremulous movements
"His nostrils palpitated"
3. palpitate, flutter
beat rapidly
"His heart palpitated"
"palpitating" in the adjective sense
1. palpitant, palpitating
having a slight and rapid trembling motion
"palpitant movements rather than violent eruptions"
"my palpitating heart"
Source: WordNet® (An amazing lexical database of English)
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