An adjective typically used to describe Vampires, Werewolves, Zombies, girls who bite you, and any vicious animal. It derives from the two words "dangerous" and "fang."
"Damn, that Jessica is Fangerous! She keeps biting random boys!"
"Oh woooww, That Bill Compton is so fangerous, I love how he looks when his fangs are out."
Oh geez! It's a snake! Be careful man! Those things are fangerous!"
This is a less offensive way of saying "smell my fingers". It's still offensive and if you are able to get someone to do it then that person is a fool. They may have been touching their butt crack doing a stink check.