IPA: /ˈhɑːt.biːt/
KK: /ˈhɑrtˌbit/
A single complete pulse of the heart, often used to refer to the rhythm of the heart or a vital force in a situation.
I could feel my heartbeat quicken as I approached the stage.
Heartbeat → It is formed from "heart" (from Old English "heorte", meaning the organ that pumps blood) and "beat" (from Old English "beatan", meaning to strike or hit). The word "heartbeat" refers to the rhythmic beating or pulsation of the heart.
Think of the heart as the organ that 'beats' — that's why 'heartbeat' describes the rhythm of the heart.