A snake from one of several species of the genus Acanthophis, relatives of the cobra, found throughout New Guinea and Australia (except Victoria and Tasmania).
A Death Adder is extremely odd-looking: small, short and fat with a triangular head and a short spiky tail. In fact, it is one of the few snakes which a non-herpetologist can tell the tail from the rest of its body.
A death adder is not an aggressive creature -- it hides in rock crevices, and in burrows under leaf litter to escape the sun and to lie in wait for prey. However, it will bite when provoked, injecting a potent neurotoxin that kills 50% of untreated human recipients. In this case, "provoked" means "stepped on", someting the snake will do nothing to stop: it has no hearing, and thinks the vibration from approaching footsteps is really approaching prey.
A death adder bite can only be treated with antivenin. Pressure immobilization is encouraged to buy time until the recipient can get antivenin.