Something thats is grows nasty or sick but there is interest and amazement in it. Then ending up being a hybrid of the word gnar and nasty which ends up gnarsty
Joe "Man have you seen the worlds biggest turd"
Darnell "Damn I aint looking at that shit you're sick"
Harold "It's pretty gnarsty I tell you
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.