The Collaborative International Dictionary of English v.0.48:

Lamia \La"mi*a\, n. [L., fr. Gr. ?.] (Class. Myth.)
   A monster capable of assuming a woman's form, who was said to
   devour human beings or suck their blood; a vampire; a
   sorceress; a witch.
   [1913 Webster] Laminaa

WordNet (r) 3.0 (2006):

lamia
    n 1: (folklore) a corpse that rises at night to drink the blood
         of the living [syn: vampire, lamia]