1) A term used to depict a time period where a lack of skill, ability, or performance was displayed. It is also used to mock people who "find the cheapway" to play games or perform tasks. This term can be used to many different types of situations.
Mom: "Rodney, your room is filthy. I thought I said clean it."
Son: "I did clean it."
Mom: "Did you clean it during amateur hour or something? This is atrocious!"
Applied to School:
Professor: "The class average was a D+ on this exam...seriously class, is it amateur hour when you all come here?"