Revenant is really a broad term that’s used to differentiate a reanimated or wandering corpse from a vampire. But, the word is from the French “revenir,” meaning “to come again,” and implies that a revenant is somebody that has returned from the dead. Our modern day dictionary says it‘s, “a person who returns as a spirit after death; ghost.” So, in a way it can be used to describe a vampire, it just depends on how nit-picky you are.
While some may think a revenant does in fact mean vampire, the truth is it was originally used to describe a restless ghost or spirit that constantly returned to the scene of a terrible occurrence, like a bloody murder or crime scene, where he/she was originally killed or where they killed someone else. It was said that these ghosts could find no rest until an exorcism was performed. So while dead, they weren’t vampires by any definition.
The Greeks on the other hand viewed revenants as a reanimated body of a loved one. These revenants weren’t violent though, not unless they were extracting revenge that is.
This definition could actually be used against most vampire cases reported in the Middle Ages and in the treatises of the seventeenth and eighteenth centuries when many of their returning dead, or what they called vampires, were pretty nonthreatening. Then the Church did their meddling and clarified its position on excommunication and the supposed infestation of a corpse by evil spirits, this triggered the sinister outlook on revenants, which were later confused with vampires.
So, are vampires revenants? I suppose it really depends on what definition you choose to use. Technically calling a vampire a revenant isn’t wrong, so go right ahead. Woo!