Top Definition
A 'fourthy' is a partial erection. One might be apt to call it a half-boner, but this would be technically incorrect as a 'fourthy' occurs when a penis is more than 1/4th of the way up...hence, a fourthy.

It should be noted that fourthies (plural form) are apt to occur at inopportune times (such as in public places) and as such are typically surpressed to prevent a complete erection.

If a complete erection does take place, it would be said that 'he has a boner', not a 'fourthy'.

In most cases fourthies are largely unsightly however exceptions are known to occur.
OMG that milf gave me such a fourthy.

Joey's such a pussy, when she kissed him on the cheek he got a fourthy.
by tmkly3 October 15, 2007

The Urban Dictionary Mug

Lotsa space for your liquids.

Buy the mug

The Urban Dictionary Mug

Lotsa space for your liquids.

Buy the mug

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