Pulling a Pendergast is a term used when a player goes public with a clue for Halliday's Hunt.
It is named after Steven Pendergast, a "loudmouth MIT freshman" who found a hidden message in Anorak's Almanac, and released it to the public for "his 15 minutes of fame".
The world named the message "The Limerick", and knew about it for around 4 and a half years before the Egg was found.
According to the book, it's a stupid thing to do.