mad as a cut snake

adjective2

1. •
   (Australia, informal) Very irate, crazy with rage.

   • I′m feeling slightly less furious than I was earlier, but I′m still about as mad as a cut snake. — 2005
2. •
   (Australia, informal) Crazy; eccentric.

   • “Trackless,” Sean muttered, “there′s a man over there planting a chopstick.″ “Him? That′s Lurker. Mad as a cut snake.” — 1986