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Phrase(s): 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.
McGrawhill's American Idioms And Phrasal Verbs
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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.
American Heritage Idioms