A 50 pounder is a consultant or advisor that gives unsolicited and useless advice, with the ulterior motive of getting paid for his apparently "quality" services. He is a salesperson, good with words, that can trick a naive person.
The 50 pounder is actually skint and has very little money in their bank account (about £50). When confronted, the 50 pounder gets aggressive due to his/her fear of being exposed.
To be avoided via good bullshit detectors and due diligence.
Dude, stop talking to him. He's a scam and his greatest achievement was only to be a 50 pounder.
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?"