It means that if you bitch loud enough, you'll eventually get your way.
Becky begged for months to her parents for a new car and she somehow got it. Squeaky wheel gets the grease, I guess.
de KRHimself 20 juillet 2005
1 more definition
Only the loudest whiner gets what he wants. ("The wheel that squeaks the loudest / Is the one that gets the grease.")
We all wanted the last bit of water, but since Hector whined all afternoon about being parched, Dad gave it to him. I guess the squeaky wheel gets the grease.
de J Basc 5 décembre 2007