When a lad you love cheats on you just when you feel secure, he has pulled a Beatties on you!!!
B/F: I love u hunny bunny purlease never leave me!
G/F: O...K... whatever!
*months down the line*
G/F: Oh Im glad im with him he really is nice!
*B/F shacks up with uber fat chic from Beatties!, Ooooooooh how DEGRADING*
Derived from the word "Bitty" however this describes a girl who has been beat with the ugly stick. "Beatty" is often used to describe an ugly bitch. They tend to be friends with bitties, but in reality they are only kept around to make the true bitties look better.
Dude, I am at the party and the one hot chick is guarded by a beatty. Not zef. GTFO