when a girl thinks she is extremely hot, and puts a bunch of pictures of herself (and sometimes friends) in their bikinis on facebook to show off.
Casey and Marissa changed their facebook profile pictures to the bikini shot they took at the beach. With their cleavage perfectly tanned and their belly's firm, all they could think of was "Dayy-um! We're hot!"
"Yo do you see that bikini sideburn?! It's like Cousin Itt moved in!"
"From the looks of that bikini sideburn, she's waiting for the bird's eggs to hatch!"
"That Bikini Sideburn looks like Hulk Hogan's hairline!!!!! SICK"
When two (or more) girl friends with different colored bikinis swap their tops so that they're matching. Used especially on social media to show that they're best friends.