The dictionary basically says that tepid is luke warm. when tepid is used in a sentence it usually refers to how its not cool at all, and its not hot either.
Bro check out my walk-man! Its so sick!
dude, thats like totally tepid
Dude, my new ipod is so cool!
that new album by rihanna is so hot!
1. When it is not quite phat and it's not quite honkified. It's tepid.
2. When shit is just totally beyond the point of being hot, it's TEPID.
2. Did you hear that new 50 Cent joint? Yeah, I heard he wants to make a change. Yeah, that shit was tepid.