"gnarly" is an old teenage slang term from the eighties and means more "hard or difficult"... for example... "that test was really gnarly" or for surfers "a gnarly set of waves". (I"m from California) If someone is bad tempered, I would say they were grumpy, irritable, or cranky.

Yeah, I just posted about this on an identical thread. That expression is horrid. I would have said it was out of the 90s because I'm 59 and grew up in California. We didn't say that in the 70s. And, I don't recall hearing it in the 80s, but it might have been said then, but then I was in my 20s. I agree I think that monstrosity of an expression came out of some California high school some place, probably in the LA area. Thank god it's dying out. I totally forgot what it meant since I haven't heard it in 20 years. Mean-spirited, hot headed, a hot head, having a short fuse, are all like bad tempered too.

"gnarly" is an old teenage slang term from the eighties and means more "hard or difficult"... for example... "that test was really gnarly" or for surfers "a gnarly set of waves". (I"m from California) If someone is bad tempered, I would say they were grumpy, irritable, or cranky.