Baseball is the American bat-and-ball game in which a batter hits a pitched ball and runs round four bases. A baseball game, a baseball bat, the baseball season.
It is the national sport of the United States and largely unwatched elsewhere, though it is big in Japan, South Korea and much of the Caribbean. Its vocabulary has escaped into general American English more than any other sport's: ballpark figure, out of left field, touch base, step up to the plate, three strikes. A British speaker will meet those phrases long before meeting the game, which is worth knowing when they turn up in a business meeting.
1nounbaseballAn American game in which a batter hits a ball and runs round four bases.
“He played baseball at college and nothing since.”
2nounballThe ball used in that game.
“A baseball went through the greenhouse roof.”
Too few real examples of this word to estimate which sense is commonest.
baseball is a sport.
From base + ball.
Etymology from Wiktionary, CC BY-SA