If something's pulsing like a heartbeat, it's throbbing. When you stop and catch your breath after a long run, you might hear your throbbing pulse in your ears.
An injury that's throbbing with pain pounds with regular beats: "I have a throbbing headache." Music is often described as throbbing too, beating and pounding with deep bass notes from a club or a car — or maybe your ceiling is vibrating with the throbbing music your upstairs neighbors are playing. To throb is to pulsate, and experts guess the word itself stems from the sound and feeling of pulsating blood.