Synonymous to 'insane' or 'blow-your-mind-awesome'. Very popular in the Midwest United States, and is frequently used when speaking through a public address system.
The word is often associated with events happening on Mondays, thus forming the phrase, "matatical Monday".
Hey bro, what happened to you?
Don't know man, but I sure had a matatical Monday night...
Woah, you did that crazy stuff on a Monday night? that's pretty matatical, bro. I was just doing homework all night *sigh