To be completely and utterly fucking crazy. It can be used to describe a noun. Mostly used to emphasize the emotional state of a person.
The teacher didn't completely erase the notes on the chalkboard, which caused obsessive-compulsive Isaac to go batshit loco and turn over his desk.

I don't know what the fuck happened, all of the sudden he went batshit loco and shit on the couch!
by Capt. Win October 3, 2007
Get the Batshit loco mug.
Past the point of insanity, past the point of rationality. Incorperates both the meanings batshit and loco but on a much higher scale. Just losing it, the day before or maybe the day you are commited permenantly to a mental asylum.
Jim: Yo dude, whats up?

John: Not much, dave's nailing hamsters to the wall in the kitchen

Jim: WTF?!? what for?

John: His girlfriend left him for his brother, He's gone completely fucking batshit loco
by Yanosh February 19, 2006
Get the Completely fucking batshit loco mug.