People who break the rules of the New York City Transit Authority for their own benefit. This is usually illegal, as it involves stealing MTA property, and/or trespassing. This includes breaking into the cabs of subway trains, peeling stickers off of buses, or changing the route signage on trains without permission. It also often causes confusion in the system.
Conquesters don't usually admit their wrongdoings, and usually claim to be "civilized transit enthusiasts."
Foamer: *removes poster from subway station for an active service change*
Railfan: OMFG YOU CONQUESTER! WHY WOULD YOU STEAL THE POSTER!?!
Foamer: It's for the collection. Now leave me alone, since I'm just trying to enjoy the trains and I don't need your ass annoying me.
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?"