Homonym: curveball (Unexpected)
A "curveball" is a type of pitch in the game of baseball that is designed to deceive the batter. It is thrown with a specific grip and wrist action that causes the ball to spin in a way that makes it curve as it approaches the plate. This movement can make it difficult for the batter to predict where the ball will cross the strike zone.
In a broader context, the term "curveball" is often used metaphorically to describe an unexpected challenge or surprise in life. Just as a batter must adjust to a curveball pitch, people must adapt to unforeseen circumstances that can change their plans or expectations.