The uncanny ability for people who are not quite right in the head to have sometimes supernatural strength. Particularly when they are wound up from you calling them a retard.
"Was abusing mental sheppy the other day"
"Fuck that mate, hes got proper mongstrength"
Mong strenght is when someone use a surprising amount of stength when they get angry, like a mong when they dont get there afternoon pills! When someone gets mong strength they can do things they couldn't normaly do, e.g. punch harder, flip heavy tables, smash/brake strong things.
"Did you Bill yesterday, someone called his mum a slut so he got mong stength, n stated flippin tables!"
Pajama casual is a term used when working from home and preparing for a video conference. All business above the waist and your pajama pants down below.