butter side up
Ass (butt) in the air, posed, waiting for sex. Sexual position.
I flipped her butter side up.
buttered side up
An expression meaning that everything turned out alright like your toast landing buttered side up.
Her: It's been a rough year, a breakup, lost my job and my best friend..
Me: Chin up, you'll land buttered side up! You always do!
Me: Chin up, you'll land buttered side up! You always do!