Definition of alastor:
(n) :
An avenging spirit or deity, variously associated with the Erinyes, Nemesis, and more.
(n) :
In more recent ages, a term of rebuke for a pestilent rascal.
(n) :
(entomology) A genus of hunting wasp
(n) :
A male given name from Scottish Gaelic.
(n) :
(Greek mythology) Any of several characters in Greek mythology, variously spirit, human, a horse of the underworld.