All 12 Uses

limerick
in
Ready Player One
(Auto-generated)

Once the message became public knowledge, gunters nicknamed it "the Limerick."
The Copper Key awaits explorers
In a tomb filled with horrors
But you have much to learn
If you hope to earn
A place among the high scorers
p. 65.9 *

limerick = a 5-line poem with a rhyme scheme of aabba
So I devoted an entire section of my grail diary to deciphering the Limerick, line by line.†
p. 66.1
From the moment I saw the title, I was certain the second line of the Limerick was a reference to it.†
p. 66.3
But that was the rub: The Limerick didn't appear to give any hint as to where Halliday had hidden the damn thing.†
p. 67.1
If any other gunters out there shared my interpretation of the Limerick, so far they'd been smart enough to keep quiet about it.†
p. 67.8
" Hearing her repeat the phrase "to learn" was enough to make me think of the Limerick.†
p. 68.5
What if the Limerick was saying that the tomb was hidden right here, on Ludus?†
p. 68.9
The Limerick might refer to one of them.†
p. 69.3
I wasn't the first gunter to decipher the Limerick and find the Tomb of Horrors.†
p. 88.6
It had taken me years to decipher the Limerick and locate the Copper Key.†
p. 113.4
You deciphered the Limerick on your own, otherwise you wouldn't even know about the Tomb of Horrors module, right?†
p. 124.5
At least two other gunt ers were sharp enough to connect the dots between Ludus, the Limerick, and the Tomb of Horrors.†
p. 129.1

Definitions:

(1) (limerick)
a humorous poem consisting of 5 lines with a rhyme scheme aabba

Limericks often have a 9-9-6-6-9 or 8-8-5-5-8 cadence and are ridiculous. Often they are slightly indecent.

Here is an example of a tame limerick:

There once was a man from Nantucket
Who kept all his cash in a bucket.
But his daughter, named Nan,
Ran away with a man
And as for the bucket, Nantucket.
(2) (meaning too rare to warrant focus)
As a proper noun, Limerick usually references a city or county in Ireland.