Blowing air out my nose. Similar to "LMAO" used to describe that laugh you do when something is funny but not funny enough to laugh out loud and you just "blow air out my nose".
Text message:
"Why did the Chicken Cross the road? To get a gallon of milk."
"BAOMN!!!"
"Totally a BAOMN joke."
"BAOMN indeed."
Boaon(Bit Of Air Out Nose) or aon(Air Out Nose for short) is to demonstrate the true thing you do via an instant messaging program when you supposedly lol(Laugh Out Loud). When you merely snuffle a little bit other than actually laughing out loud.