Longman Dictionary of Contemporary English
baseball cap
noun
EXAMPLES FROM CORPUS
▪ He had a round face and was wearing a baseball cap.
▪ He reaches the ball a step ahead of an agile sprite named Molly, whose ponytail flows behind her baseball cap.
▪ One boy is slouched down in his chair, wearing a baseball cap, the bill turned backward.
▪ One person decides to wear a baseball cap back to front, and then others do likewise without bothering to ask why.
▪ The man in the baseball cap was moving through the crowd towards us.
▪ The prime suspect is a man in his 20s, who wears blue overalls and a red baseball cap.
Wiktionary
baseball cap
n. A cap with a rounded crown and a curved, stiffened bill at the front.
WordNet
baseball cap
n. a cap with a bill [syn: jockey cap, golf cap]
Wikipedia
Baseball cap
Usage examples of "baseball cap".
He had extracted a promise from her that she'd wear a kerchief or a baseball cap over the dye-job, but promises were made to be broken.