From Spanish (mostly used in Spain), a derogatory word for someone with down-syndrome (Mongolism); English equivalent of mongo. It also can be used for retard, dumbass, spasty, jerk, junkhead etc. Mostly describes a person with very low IQ and behaving stupidly all day.
Que te pasa? Eres mongolico? What's wrong with you? Are you a mongo (mongolico)?
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?"