jack-in-the-box

American  

[jak-in-thuh-boks] / ˈdʒæk ɪn ðəˌbɒks /

Or jack-in-a-box

noun

plural

jack-in-the-boxes

1. a toy consisting of a box from which an enclosed figure springs up when the lid is opened.

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jack-in-the-box British  

noun

1. a toy consisting of a figure on a compressed spring in a box, which springs out when the lid is opened

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Etymology

Origin of jack-in-the-box

First recorded in 1545–55

Example Sentences

They discovered that the TCR behaves like a jack-in-the-box, staying compact until it encounters an antigen or another suspicious particle, at which point it rapidly opens.

From Science Daily

With their aid, she rose like a jack-in-the-box, swaying unsteadily as her eyes adjusted to the light.

From Literature

Like a jack-in-the-box, Old Timothy had popped up from nowhere.

From Literature

When I’m gone, they tuck her in, and at 2 a.m., when she pops up like a jack-in-the-box, giggling and whining, they sit with her until she exhausts herself and falls back to sleep.

From Salon

Pakistan's jack-in-the-box surprise element now feels akin to a cliche from a bygone era.

From BBC