To do more work than nesscary, like when someone flexes their back more than needed to do something.
This phrase is usually assoicated with doing with doing extra credit homework or taking 2 hours to work that can easily performed in 30 mins, generally all schoolwork that geeks and nerds do.
Me:How many of pages of coursework you do? I did 9, font size 14
Zubair: Man I was up till 3 in the morning and did 33 pages, font size 10.
Me: Your long flex dude.
4👍 10👎