inclined to lustfulness; wanton; lewd; arousing sexual desire; indicating sexual interest or expressive of lust or lewdness.
Collarbones are sexy and basically what is said above. ;D
a more discreet way of telling someone you have an eating disorder (mostly used by people that suffer from anorexia or bulimia).
sometimes, if you get very thin or lose a drastic amount of weight, you'll see that most people's collarbones are a bit crooked. something you won't notice on non-thin people.
may sound stupid if the person you're talking to doesn't know this, but it can help just trying to say it out loud more discreetly in the beginning.