Top definition
To insert an object into ones penis (urethra) to gain pleasure or because one is a masacist. Anytime an object is inserted in the penis not for medical reasons.
If you start penis knuckling you may injure you urethra due to its soft interior.
by Mr. Johnny Hammerballs March 16, 2010
Mug icon

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