Palpitation (noun)

A noticeable or irregular beating of the heart, typically caused by stress or anxiety.

Origin:

Late middle english: from latin palpitatio(n-), from palpitare "to throb, beat strongly".

Examples:

1. She felt a palpitation in her chest and knew she was nervous.
2. The doctor could hear a palpitation in the patient's heart.
3. The palpitation of his heart was audible and he was worried.
4. The palpitation was caused by the caffeine in the coffee.
5. She was having a palpitation and needed to sit down.