curveball
Didn’t see that one coming! A curveball is an unexpected event or something that is intended to trick someone or throw them for a loop. The term is directly based on the curveball in baseball, a pitch that curves as it approaches the batter in an attempt to throw them off so they miss. If someone throws you a curveball, it means that they gave you a challenge or difficult problem unexpectedly.
The curveball isn’t the only type of ball to enter popular slang, though.
A screwball is a person who acts irrationally or tends toward zany antics. Screwball can also be used as an adjective to describe something eccentric or kooky. In baseball, a screwball is similar to a curveball except that it curves in the opposite direction of most pitches.
A softball is something that is easy to solve or an easy problem to deal with. If someone throws you a softball, they are pulling punches and going easy on you. Softball is also the name of a sport that is a variant of baseball that uses different balls. Interestingly, the science suggests that a softball is actually harder to hit than a baseball.
On the other hand, hardball is an adjective that describes someone as being ruthless or something as being difficult. If someone is playing hardball, it means they aren’t giving an inch and are acting aggressively. The word harball is sometimes used as a synonym for baseball (especially really competitive baseball) to differentiate it from softball.