A poetic verse structure mysteriously named for a city in Ireland. An English teacher would probably say that
the form is properly described as a variant of anapestic trimeter, but most limericks have nothing to do with being proper.

There are two schools of thought on the acceptable content of a limerick. The first simply states that any poem with
the proper verse structure and ryhme scheme is a limerick, just as the same is true of a sonnet or villanelle. For example,
"Hickory-Dickory-Dock" could be a perfectly fine limerick.

However, many purists maintain that the title of 'limerick' should not be bequeathed so lightly. A true limerick must
be of content suitable to be scrawled on the wall of a disreputable men's lavatory, right under Debbie's phone number.
Knowing a few of these limericks will instantly make you the center of attention at any societal function. People will
look at you in shock and wonder if just popped in to visit from the 1890's. Then they'll forget you and get back to partying,
and you will get back to sitting in the corner, forlornly stirring the onion dip with you finger.

Personally, as per the content question, I agree with the author of this anonymous limerick:

The limerick packs laughs anatomical

Into space that is quite economical,

But the good ones I've seen

So seldom are clean,

And the clean ones so seldom are comical.