It's much like the word "crazy" but way cooler. It has many meanings. It can be used as both an adjective, verb, or noun.
Crazyguy is a very active word, full of or characterized by activity.
Crazyguy synonyms are: crooked, askew, mad, insane, impractical, erratic, being out of the ordinary, unusual, distracted with desire or excitement, passionate.
You can use crazyguy in both a good and bad way.
"Wow, you really made that part in the song so AWESOME."
"Yea, I kind of went all crazyguy on it."
"Man, Christina Aguilera really butchered the National Anthem at the Super Bowl this year. She just got way too crazyguy on it."
"I wouldn't walk by yourself around here. There's way too many crazyguys in the area."