batshit

adjective

bat·shit

ˈbat-ˌshit

vulgar slang

: very irrational, excited, or angry : crazy entry 1

Some say he's smart and some say he's permanently batshit—but they don't say it to his face … . Besides, most truly talented people are, well, strange.

Linda Ellerbee, And So It Goes, 1986

This tended to drive the real Hollywood people … absolutely batshit.

Jay McInerney, The Guardian (London), 3 Nov. 1996

—often used with go

… she shows you that you are not alone in the world, … lets you know that everyone goes batshit sometimes, and that recovering from it can lead you to expectations and views that translate to a new life, a better life.

Sridhar Pappu, The Atlantic, January/February 2005

batshit adverb

Joey is aware that there are a lot of people, … who are just batshit crazy.

David Brooks, Weekly Standard, 28 Apr. 2003

… over the years he's been called everything from ruthless to batshit insane …

Seth Mnookin, Vanity Fair, December 2008