When two lovers go nostrils to nostrils (in a 69 fashion) and then proceed to breathe. When one inhales, the other exhales. And vice versa.
Her: so what’s your kink, sugarlips?
Him: Have you ever heard of a nosey nine?
“Man I just saw some lesbians doin’ a nosey nine behind that dumpster! They must really love eachother”