British slang term- "that's sad/funny"(but I couldn't really care to be honest).
Example:
"Mate, emma broke up with me"
"ah, that's peak"
The friend hoenstly couldn't care any less, it's not their problem. It can also be used as a joke as well:
"My mum took my phone"
"Haha, that's peak"
Any dragon ball movie or series
Hey bro want to watch peak with me?
bro: Sure
peak means really sad and depressing, could also be used to take the piss out of someone
Tom: "Bro I fell over in front of my crush yesterday."
Charlie: "Mate that's peak