When you have an erection that your girlfriend doesn't know about and you whip it out of your pants and show her your hard on, usually with a really pleased expression on your face.
I was lying in bed reading the other day when Rob pulled down the sheets and sprung his jack in a box on me!
by Robertion August 17, 2011

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Top Definition
A toy. Not to be confused with "Jack in the box", a fast-food restaurant.
Baby Hugo cried whenever he played with his Jack-In-A-Box. Every time Jack popped out it frightened him. Bad Jack!
by MTF January 22, 2009

The Urban Dictionary Mug

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The Urban Dictionary Mug

Lotsa space for your liquids.

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The Urban Dictionary Mug

Your favorite word on a white mug.

Create a mug

The Urban Dictionary Mug

One side has the word, one side has the definition. Microwave and dishwasher safe. Lotsa space for your liquids.

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The Urban Dictionary T-Shirt

Soft and offensive. Just like you.

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The Urban Dictionary T-Shirt

Smooth, soft, slim fit American Apparel shirt. Custom printed. 100% fine jersey cotton, except for heather grey (90% cotton).

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A penis that looks average until it is aroused and then erects to a size well above the norm.
Andrew: Yes, my penis looks only about an inch long when it is soft.

Slampiece: Well I must admit, your Jack in a Box was a nice surprise!
by Quagmire517 September 09, 2011

The Urban Dictionary Mug

Lotsa space for your liquids.

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The Urban Dictionary Mug

Lotsa space for your liquids.

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The Urban Dictionary Mug

Your favorite word on a white mug.

Create a mug

The Urban Dictionary Mug

One side has the word, one side has the definition. Microwave and dishwasher safe. Lotsa space for your liquids.

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The Urban Dictionary T-Shirt

Soft and offensive. Just like you.

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The Urban Dictionary T-Shirt

Smooth, soft, slim fit American Apparel shirt. Custom printed. 100% fine jersey cotton, except for heather grey (90% cotton).

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When a girls fists herself and then you put your dick in too and she gives you a handy.
I went to a donkey show in Tijuana and the girl really stepped up her game by giving the bachelor a Jack In A Box.
by fucklayton September 23, 2015

The Urban Dictionary Mug

Lotsa space for your liquids.

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The Urban Dictionary Mug

Lotsa space for your liquids.

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The Urban Dictionary Mug

Your favorite word on a white mug.

Create a mug

The Urban Dictionary Mug

One side has the word, one side has the definition. Microwave and dishwasher safe. Lotsa space for your liquids.

Buy the mug

The Urban Dictionary T-Shirt

Soft and offensive. Just like you.

Buy the t-shirt

The Urban Dictionary T-Shirt

Smooth, soft, slim fit American Apparel shirt. Custom printed. 100% fine jersey cotton, except for heather grey (90% cotton).

Buy the t-shirt