It's a reference to Dana Scully in the tv show The X Files. It's when someone tries to use every exuse before the truth, to get out of something, or stick up for somebody or something.
If you get caughtcheating on your bf/gf and you try to make up every possible excuse you can think of, your bf/gf might reply: "Don't Scully me."
A sully meager is the type of guy who hasn’t seen the light of day/ touched grass in the past 6 months. He probably plays Gta, Apex,league of legends or mine craft ( only Java ) and in these games he probably just griefs you
Bro this dude on GTA was sooo annoying, he’s such a sully meager
Interviewer: "Well Mr Jones, everything seems to be in order and we are delighted to offer you the job"
Mr Jones: "Well spank my ass and call me Sally!"
Interviewer: "......"