What is the meaning of Heartbeat?

One pulsation of the heart; especially an irregular one, hence the emotion which causes it.

The rhythm at which a heart pulsates, a cardiac indicator.

A driving impulse or vital force; the vital center of something.

A very short space of time; an instant.

A periodic signal generated by hardware or software to indicate normal operation or to synchronize other parts of a system.

Source: wiktionary.org