Hella Happening Edit Meaning

1.

Could be used to say, It's really "happening", which in this case means it's really cool, it's off the hook, it's a lot of fun...just like hella cool would imply that it's really cool, hella happening could be used in a simillar context to mean pretty much the same thing...

That party was hella happening...(That party was hella cool)

See hella, hella cool, cool