heartbeat

noun5

1. •
   one push of the heart, which someone can feel or hear in the chest

   • The policeman waited for a heartbeat in vain.
   • He alone gives me such heartbeats.
2. •
   The rhythm at which a heart pulsates, a cardiac indicator.

   • If your heartbeat doesn't normalize soon, consult a doctor!
3. •
   A very short space of time; an instant.

   • The ambulance arrived in a heartbeat.
4. •
   A driving impulse or vital force; the vital center of something.

   • Music is the heartbeat of the people.
5. •
   A periodic signal generated by hardware or software to indicate normal operation or to synchronize other parts of a system.