A person or group of people you end up chatting with or befriending at a concert, that you never speak to again. You will probably just talk about said band and how great they are and compare notes as to how many times you've seen them. The friendship can begin on the beer line, on line for the bathroom or the general admission section when you are packed like sardines.
I pushed my way up to the front by myself and made concert friends
that actually held my spot while I went to the beer line.
At the bar after the show we talked to randoms about how great it was and made concert friends
In between sets we talked to the guys next to us about how awesome the band was, they made pretty cool concert friends