A limerick is a silly poem with five lines. They are often funny or nonsensical.
How to write a limerick:The first, second and fifth lines rhyme with each other and have the same number of syllables (typically 8 or 9). The third and fourth lines rhyme with each other and have the same number of syllables (typically 5 or 6). Limericks often start with the line "There once was a..." or "There was a..." Example of an 8,8,5,5,8 syllable limerick:

there once was a man from Peru
He dreamed ha was eating his shoe
He awoke in the night
From a bump in a fright
To find that his dream had come true