throw a curve

throw (one) a curve (ball)

To do something unexpected or deceptive that surprises, confuses, thwarts, or outwits one. A curve ball is a pitch in baseball intended to be difficult to hit due to its curving path. Her confidence and fact-of-the-matter answers threw police a curve during their questioning. I had only been reading the textbook instead of going to classes, so a few of the questions on the final exam really threw me a curve ball.
See also: curve, throw
Farlex Dictionary of Idioms.

throw someone a curve

 
1. Lit. to pitch a curveball to someone in baseball. (See pitch someone a curve(ball).) The pitcher threw John a curve, and John swung wildly against thin air. During that game, the pitcher threw everyone a curve at least once.
2. Fig. to confuse someone by doing something tricky or unexpected. When you said "house" you threw me a curve. The password was supposed to be "home." John threw me a curve when we were making our presentation, and I forgot my speech.
See also: curve, throw
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

throw a curve

Surprise or outwit someone, as in They threw me a curve when they said that our department would be combined with yours. This colloquial term comes from baseball, where a pitcher tries to fool the batter by using a curve ball, which is thrown with sufficient spin to make it veer from its expected path. The term was transferred to other kinds of surprise, not necessarily unpleasant, in the mid-1900s.
See also: curve, throw
The American Heritage® Dictionary of Idioms by Christine Ammer.

throw a curve

cause confusion or consternation by acting unexpectedly. US informal
Curve is short for curve ball , a term in baseball for a delivery in which the pitcher causes the ball to deviate from a straight path by imparting spin.
See also: curve, throw
Farlex Partner Idioms Dictionary
See also:
  • throw (one) a curve (ball)
  • throw someone a curve
  • pitch a curve
  • mulct
  • mulct (one) out of (something)
  • mulct out of
  • mislead
  • mislead (one) about (something)
  • mislead about
  • gotta get up pretty early in the morning to
References in periodicals archive
This is not a drill you would use for a pitcher who is just beginning to learn how to throw a curve. Whenever I hear about a thrower who has a curve ball (or any other breaking pitch), I will discover that the pitch is actually a fastball that goes inside, outside, up, or down!
It is very important for a pitcher to learn to throw a curve ball that is inside and outside.
The pole as a tool for fastpitch softball
I taught myself how to throw a curve and a knuckleball, When I heard of Hubbell's screwball, I figured out how to throw one.
The Jackie Robinson Story
Robert and Roberta can throw a curve shot to land their discs in the basket.
Flying disc mystery
If he doesn't throw a curve, he may not have confidence in it.
With two strikes, some pitchers will throw a curve ball consistently.
Getting ready for a successful at bat. (Baseball)