Top Definition
Like a hard on, it comes about when some thing is arousing, but not enough to induce a full erection.
While watching two average women make out, Jim noticed that he was sporting a half on.
by Harry T August 14, 2007

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A semi-erect penis. (See: Semi, Chub) Fifty percent of a Hard-On. A "bulge in the pants," as it were.
I often get a half-on while leering at females on the subway.
by Time4SumAksion September 06, 2005

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Lotsa space for your liquids.

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The Urban Dictionary Mug

Your favorite word on a white mug.

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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

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When a mans dick gets bigger but not hard enough yet to not be bendable either with starting to get a boner or starting to go down.
Damn that guy has a huge dick

Nah he just has a half-on
by Its_Fucking_T0m June 14, 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.

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