Fun Ratio is the ratio of fun, to the unmentionable word "Death". The more fun it is, the more likely it is to kill you. A high Fun Ratio is the best, and the word Death should never be mentioned. A high Fun Ratio is best unless your idea of a white knuckle ride, is cutting the lawn with the ride on mower on a Sunday afternoon.
"Wow, that nearly killed him, the Fun Ratio must be high, I'm having a go next"
Note the words: "it nearly killed him", and NOT 'it could kill me'.