A word originating in the San Francisco Bay Area and used by Northern Californians. It is often a symbol of one's Bay Area words. It is a word of convenience, since it can be used in many parts of speech. As an adjective, it means "a lot of, many, various." As an adverb, it means "really, actually, very, in a high degree." It may also mean "I agree."
It may be useful to note that the expression "hella days" usually denotes a length of time much longer than several days.
"I just saw hella people running out of that building, is there a fire?"
"I ate too much. I'm hella full right now."
"That was the best night of my life."
"Hella! Me too."