A limerick is a five-line rhyming verse, usually humorous, often earthy and rude. Various limericks have appeared previous postings in this blog -- this one comes from the online journal Parody -- Poetry for the world as it really isn't.
I found Norwood's sexist limerick here in a July 2013 posting in Parody. Here is a link to previous postings in this blog of mathy limericks.