From Longman Dictionary of Contemporary Englishbaseball capˈbaseball ˌcap noun [countable] 
DCCa hat that fits closely around your head with a round part that sticks out at the front
DCCa hat that fits closely around your head with a round part that sticks out at the frontExamples from the Corpus
baseball cap• One person decides to wear a baseball cap back to front, and then others do likewise without bothering to ask why.• One boy is slouched down in his chair, wearing a baseball cap, the bill turned backward.• 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.• The prime suspect is a man in his 20s, who wears blue overalls and a red baseball cap.• The man in the baseball cap was moving through the crowd towards us. 