A palpitation is when your heart beats quickly and irregularly. It's also any kind of shaky, quivery motion.
You know how your heart goes a mile a minute when you're excited? Then you've felt palpitations: that's when your heart beats fast and out of rhythm. Palpitations can be nothing serious or they could be signs of heart trouble. Also, a palpitation is any type of shaky motion, such as quivering or trembling. People with Parkinson's disorder have a lot of palpitations, and we all have palpitations — such as shaky hands — when we're nervous.