What is the definition of a "Femme Fatale"?

One of my favorite authors of Harboiled Noir is Vera Caspary who in Thelma or Laura gives examples of what I think is this type of character? Could the members of this group come up with a definition of the "Femme Fatale" illustrating it by examples in literature?

Literally, I suppose a woman who lures man to do something that is his undoing, even his death or near death, like Bridget in the Maltese Falcon or unfaithful wife in Double Indemnity.

thak you Artymedon and quartzite to reply
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One detective - I can't remember who - described one as "blond - with legs that went on forever".