Down to Earth; Authentic. Typically defined by not letting wealth or fame make you forget who you are and where you came from. In the context of relationships, it means that you stayed true to your significant other and did not cheat or break their trust. It can also mean that you don't let things like social status or economic status change the way you treat a person.
Used by students of the Mercedes class of 2006. It evolved from the use of sarcasm. i.e. When someone says something that is unfavourable, the response is 'real'.
Person 1: We have to stay behind after school until we finish our assignment!
Person 2: Real! Like we're gonna do that
OR
Principal: If anyone is involved in vandalising the school on muck-up day, they will not be allowed to sit their exams here.
Yr 12s: (muttering to eachother) Real!