Can be used in any positive way. If something is 120 it is
the greatest thing ever. If someone is 120 they are
better than the best. If you did something 120 then you couldn't have done it better. It can be used as encouragement; if someone is doubting themselves you can say hey 120,
you got this. Basically it is a noun verb adjective adverb and anything else meaning the best.
I can't believe you just climbed
mount Everest without any help. Thats so 120.
Jessica said the funniest thing the other day. She is 120.
Sam: "Ugh I can't run another
mile." Me: "Yes you can dude, 120!"