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curve ball

1. In baseball, a ball that curves in its trajectory toward home plate. He's a good batter, but he has a hard time hitting a curve ball.
2. An unexpected occurrence or thing that causes confusion or uncertainty. I thought I had confirmed my hypothesis, so these results are a real curve ball.
3. A deceptive action or thing. I don't know, I think her sudden displays of affection are just a curve ball to get me to trust her.
See also: ball, curve

throw (one) a curveball

To introduce a problem piece of information that shocks, bewilders, or confounds one or makes it more difficult for one to succeed. An allusion to baseball, in which a curveball is a pitch that arcs toward the batter in order to be more difficult to hit. Primarily heard in US. The end of that trick always throws the audience a curveball. I love watching their faces as they desperately try to figure it out. It really threw Stu a curveball when Olivia announced she was leaving the company.
See also: curveball, throw
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

throw somebody a ˈcurveball

(American English) surprise somebody with a problem, situation, question, etc. that they do not expect and which is difficult to deal with: Just when you think you have it all under control, life throws you a curve ball.
In baseball, a curveball is a ball that is difficult to hit because it does not move in a straight line.
Farlex Partner Idioms Dictionary © Farlex 2017
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References in periodicals archive ?
"You could hear Blyleven's curveball. I played with him in Minnesota, but faced him when I was in Baltimore.
Then comes the curveball, the pitch that makes you swing when you shouldn't.
There are other ways to throw curveballs at the bucks you are hunting.
Cease throws faster than a normal pitcher while also mixing in a curveball and change-up.
"I saw him throw a curveball to me a little earlier that kind of floated, so I knew it was coming again,'' Solomon recalled.
Kudos to Reynolds for throwing such a career curveball, however.
Pitchers throw various types of pitches (fast ball, slider ball, curveball, changeup ball, other) to strike a batter out and to keep most hitters off.
However, they didn't count on the curveball that was FBI Agent Pike.
The Internet giant is said to have ordered up two new search-related initiatives, codenamed Fast Break and Curveball.
I would just pick the cast of Emmerdale to really throw the Germans a curveball. Lisa Dingle up front on her own?
The story opens in the tiny town of Brittle, Nevada and grabs reader attention with Coco's first-person discussion of a pivotal moment in life: "Once in a blue moon life throws you a curveball you never see coming.
CHARLIE SHEEN: Curveball; Warlock edict; pain & devastation in Japan demands us all to dig deep & LOVE THEM VIOLENTLY
We begin with a curveball: This weekend's most interestingly Jewish announcement is not technically Jewish at all.