Bonkers means mad, in British informal use. Go bonkers, absolutely bonkers, that is bonkers.
It is light-hearted and applied to situations far more than to people, which keeps it clear of being a comment on mental health. Stark raving bonkers is the full form. It has no singular and never appears before a noun.
1adjectivebonkersMad, in British informal use.
“You're driving to Scotland tonight? That's absolutely bonkers!”
bonkers is a state.
Also accepted in games: barmy
Of unknown origin, British, from the mid twentieth century, perhaps from bonk, a blow on the head.
unknown. Perhaps from bonk (a blow or punch on the head, compare whacky); perhaps related to earlier bonce.
Etymology from Wiktionary, CC BY-SA