Definitions for vampire bat
Random House Webster's College Dictionary
any small New World tropical bat of the family Desmodontidae, having specialized front teeth for cutting into the skin and drawing blood from resting animals.
any of several other bats, esp. those of the family Megadermatidae, erroneously believed to feed on blood.
Origin of vampire bat:
vampire bat, true vampire bat(noun)
any of various tropical American bats of the family Desmodontidae that bite mammals and birds to feed on their blood
A small flying mammal (bat) of South America which uses its teeth to nick larger animals while they are asleep, allowing it to surreptitiously lap a blood meal.