A hot charlie is anything you want it to be. Because of the way it sounds, most people (especially girlfriends) associate it with something sexual (i.e. Dirty Sanchez). Simply ask for a hot charlie, and the other person must determine what his/her definition of it actually is.
Me: Hey, I'm going to ask my girlfriend if she wants to give me a hot charlie tomorrow night after the movies.
When you're hitting a girl from behind, leave for a second to somehow heat up your dong, and then return to stick it in her butt. It's customary to yell "Hot Charleys for everyone!" right after this.
P: Why are you wincing?
M: I steeped my penis in hot water too long and burnt it. Hot Charley!
While our lifespan is the number of years we will live, our healthspan is the number of healthy years we will have and our sexspan is is the number of years we will continue to be healthy enough to continue having an active sex life.