Pep is a high spirited kind of energy. It takes a lot of pep (and pom-poms) to be a cheerleader.
Watching a school play in which the actors are full of pep is a lot more fun than seeing lethargic performers halfheartedly go through the motions. After a good night's sleep and a cup of tea, you might have plenty of pep to start your day — but it might take your older sister longer to truly wake up. Pep first appeared in 1912, as a shortened form of pepper, which once meant "moxie" or "gusto."