jumping bean

American  

noun

1. the seed of any of certain Mexican plants of the genera Sebastiania and Sapium, of the spurge family: the movements of a moth larva inside the seed cause it to move about or jump.

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jumping bean British  

noun

1. a seed of any of several Mexican euphorbiaceous plants, esp species of Sebastiania, that contains a moth caterpillar whose movements cause it to jerk about

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Etymology

Origin of jumping bean

An Americanism dating back to 1885–90

Example Sentences

He calls it a cross between a ping-pong globule and a Mexican jumping bean.

From Time Magazine Archive