A heartbeat is the rhythmic beating of your heart.
When we talk about someone's heartbeat, we usually mean their pulse rate, or how fast and strong their heart is beating. But sometimes we use the phrase "keep the heartbeat" to describe keeping an activity or a project alive and moving forward. It might also mean maintaining a good flow of information or ideas in a conversation or meeting. When you're working on a team, it's like making sure everyone stays connected and keeps the energy going, so to say you're keeping the heartbeat of the project.
One pulsation of the heart; especially an irregular one, hence the emotion which causes it.
Example: He alone gives me such heartbeats
