Vampires are...

1. A blood-sucking ghost; a soul of a dead person superstitiously believed to come from the grave and wander about by night sucking the blood of persons asleep, thus causing their death. This superstition is now prevalent in parts of Eastern Europe, and was especially current in Hungary about the year 1730.

The persons who turn vampires are generally wizards, witches, suicides, and persons who have come to a violent end, or have been cursed by their parents or by the church, --Encyc. Brit.

2. Fig.: One who lives by preying on others; an extortioner; a bloodsucker.