The person that you could've and should've ended up with but didn't, usually because of a series of poor choices on your end. You pine over them and wonder what could've been all the while stalking them through mutual friends and on facebook, becoming extremely jealous over anyone that looks twice at them. You try to express your regret but they usually won't believe you unless you do some sort of grand gesture. The one that got away is someone that you will forever regret. In other words Trevor Sharod White.
I should've treated Roddy better, he is definitely the one that got away!