1. Sometimes used in England and Australia as a synonym for "Friend".
2. A movie my friend who I will call L and her sister who I will call A made and it was really bad but funny to watch because we played like every character and we tried to feed A to a vicious chipmunk and it was very mental but fun.
L, A and I: Hahahaah
L and A's mom: What are you laughing at
Originating from a certain public school which might be somewhere in the south of England perhaps, this is usually shouted at someone who has none. When yelled, it means "aha, you have no friends."
After a bad joke: "Oh, mates Jim."
OR, when talking about someone, "oh yeah, Jim has mates."
Except we come from good backgrounds therefore know nobody by the name of Jim.