n. 1) A person, often female, who is so shallow and spiritually empty, so obsessed with appearance and minutia of life, so absent from the larger issues of human existence, that she actually represents an existential danger to those she comes into contact with - specifically those she engages in romantic relationships. At first, the vapula may feed off the soul of her victim, and become slightly more intelligent, engaged in life, etc. But over time she'll simply reduce her lover down to her own level, leaving him a shell of a human being, incapable of trusting, feeling love, or mustering any strong emotion at all. At that point, he has nothing else to offer her, and the vapula moves on.
2) my ex girlfriend.
Trish is such a vapula; she gets a boyfriend, parrots his opinions until they're used up and then dumps them.