a.) The oh so glorious act of sniffing the essence of your manliness, oozing with the soul of the history of men on Earth over centuries.
b.) Catching a whiff of your balls or pubes after scratching it.
c.) What follows a good kambyo.
Guy 1: The fuck, bruh? Don't man sniff here. We're in a public place.
Guy 2: Sorry. Can't help it. Just have to. Wanna try? *hands out his fingers*