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1. Of an animal, especially a horse, to rise up on its hind legs and raise its fore legs into the air. My horse reared up when a mountain lion ran in front of us, throwing me to the ground. I froze when I saw the bear rear up in anger.
2. Of an issue, problem, or topic, to appear, arise, or present itself very suddenly or unexpectedly. We finally fixed the leak, but now an issue with the control valve has reared up. We've had a few setbacks rear up during production, but we managed to get around them all in time for the original launch date of the device.
1. Lit. [for a horse] to lean back on its hind legs and raise its front legs, assuming a threatening posture or avoiding something on the ground such as a snake. (See also rear back.) The horse reared up suddenly, throwing the rider onto the ground. When the horse reared up, I almost fell off.
2. Fig. [for something, especially a problem] to raise up suddenly. A new problem reared up and cost us a lot of time. A lot of new costs reared up toward the end of the month.
1. To rise on the hind legs, as of a horse: A rattlesnake slithered out from behind the bush, and the horse reared up.
2. To arise or appear suddenly or unexpectedly: We can handle any problems that rear up.