What is it called when a snake bites you but doesn't inject any venom?

It is called a 'dry bite.' Many times rattlesnakes, especially older and 'better educated' will not inject venom but, instead, give a warning bite. Snakes do not want to waste venom on something they cannot eat and will only inject it if they feel a life and death threat. The snake needs the venom to catch food and does not waste it on nonfood animals.