The way by which a man measures his level of fitness. If his body mass becomes too large he will not be able to see his penis
in which case he is overweight; however, if he is able to look down and see his penis, everything is good.
Wife: "You are putting on too much weight."
Husband:(Looks down and sees Penis) "Nope I'm good, my penis to mass ratio is normal."
Doctor: You need to lose some weight if you want to stay healthy"
Patient: "I thought so to, but I got a boner this morning and my penis
to mass ratio seems fine."