A Short-Sleeved Genius is a person, usually a male, who abuses their minor managerial role within a business setting. This person utilizes their limited power to assert complete authority or assumed knowledge in an aggressive manner. Think a psycho Pep Boys manager or Dwight from The Office. While anyone wearing short sleeves and a tie is a potential Short-Sleeved Genius, it is not a mandatory dress code.
I was at the DMV getting my license renewed when some Short-Sleeved Genius told me I was in the wrong line. He threatened to "write me up" if I didn't change lines. WTF, I don't even work there!
A very unattractive, creepy guy at bar, who lurks, watches, and looks for women to hit on. He is also the unattractive, creepy guy on the dance floor who will attempt to dance with you multiple times and never get the hint that you don't want to.