спятивший

1) General subject: as nutty as a fruitcake, balmy on the crumpet, barmy, barmy on the crumpet, barmy on the crumpet (с ума), beany, cracky, gaga, mad as a March hare, mad as a hatter, nuts, off (one's) conk, off (one's) crust, off (one's) trolley, off (one's) trolly, off (out of, one's) head

2) Colloquial: barking mad (from the image of barking like a mad or uncontrollable dog), batty, cuckoo

3) Jargon: balmy, bonkers, dippy

4) Simple: crackers

5) Makarov: as mad as a March hare, as mad as a hatter, light in the head, off (one's) head, out of (one's) head

6) Phraseological unit: come unhinged