Happy New Year, Everyone!

On this, the first day of the first year H.E., we must recognize the righteous folks at Turner Classic Movies who schedule the annual Marx Brothers’ marathon. Watching Animal Crackers, I was struck by the line sung by Groucho (blessed be he), “I hate a dirty joke, I do, unless it's told by someone who knows how to tell it.”

So, here’s a new year’s Comedist question for everyone, “What is a dirty joke?” The obvious answer is a joke about sex. But surely not every joke about sex is a dirty joke. Suppose the sex is mentioned, but not referred to as in:

Knock, knock.
Who’s there?
Fornication.
Fornication who?
For an occasion like this, black tie is optional.

Or suppose it is referred to, but not mentioned:

I went to the Frito-Lay factory and took the tour because they said there would be free samples, but all I got was a lousy bag of Fritos.

Or suppose it is a joke where the punchline is based on the lack of expected sexual content as in the classics:

Farmer Brown had a cow and decided it was time to call his neighbor to bring over his bull. The neighbor sent his daughter to take the bull over to his neighbor’s. Farmer Brown’s son stood next to his neighbor’s daughter and as the cow and the bull got on with their business, he turned and said to her, “You know, that makes me want to do the same thing.” Looking up, the farmer’s daughter replied, “Go ahead, it’s your cow.”

Or the related,

Sol Rosenberg turns 90 and as a surprise his friends sent a hooker to his room in the home. Taking off her coat she says, “I’m here to give you super sex.” “What?” says Sol. A little louder she says, “I’m here to give you super sex.” “Huh?” Sol asks. Louder still she says, “I’m here to give you super sex.” Looking up, Sol replies, “If it’s alright, I’ll take the soup.”

Are any of these dirty jokes? What is it that makes a joke dirty? And if you don’t know, what’s your best?