a combination of the words 'badonk-a-donk' and 'binoculars'. basically, a tool used by those with bad vision to verify if a girl has a nice ass from a distance.
"hey man, check that girl out, she's a looker!"
"eh, i dunno, better get out the badonkulars, just in case..."
Sounds like "Binoculars". Like Beer Goggles for staring at a woman's ass, typically a chick with a flat or weird shaped ass, that looks amazing when drunk.
Dude 1: "bro you were grabbing flatty Maddie last night!"
Dude 2: "I don't give a flying fuck, I saw her with my badonkulars on!!"
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.
FRIEND A: "Did you just take a stealthie of me?"
FRIEND B (turning phone around): "no I was just using snapchat's new filter, see?"