A pun is an unfunny play on words, either using similar sounding words (homophones) or using different senses of a word.
For example: Very punny.
The pun, of course, is a federal offense, and those who practice the art of punning are usually child molesters. A punster judges the effectiveness of his or her work by the volume, amount and pain of the groans of the audience, the number of times he or she is struck by people and the quantity of food scraps hurled at them in appreciation of their talents. Most punsters die cold and alone, which is why this wiki was made, so that the punsters here will still die cold and alone, but they will die with the knowledge that plenty of other dipshits will die cold and alone with them.
A man walks in on another man having sex with a dead pig. The first man, appalled asks what in blazes the second man is doing. "I'm porking it," replies the second man, and proceeds to cum on the first man's face.