When you start acting like a mong/retard when you get hyper. Typically seen in people with ADHD or Autism. Sometimes caused by sugar but can also be caused by girls talking to the person.
Charlie : Hey Robbie, what's happening with (insert name here)?
Robbie: Oh he's Yousefing, maybe because he ate a Mars Bar or a fit girl maybe said Hello to him.
Charlie: Alright I'll stay out of his way for a few hours, thanks for the heads up.
somethingredundant that yousef usually says or asks. he usually says it after someone said the same exact thing 2 seconds before him.
random student-"what's a variable?"
teacher-"a variable is a symbol that represents a quantity that may assume any given value or set of values."
2 minutes later:
yousef-"what's a variable?"
teacher-"Heh there you go with your yousefisms."
class-"Hahahahahahahaahahahahahahaahaa"
Using stolen gasoline to burn local parks, specifically playgrounds.
Yousifing is a term used to describe when gasoline is specifically stolen, to commit arson.