The Collaborative International Dictionary of English v.0.48:

Sylph \Sylph\, n. [F. sylphe, m., fr. Gr. ? a kind of grub,
   beetle, or moth; -- so called by Paracelsus.]
   1. An imaginary being inhabiting the air; a fairy.
      [1913 Webster]

   2. Fig.: A slender, graceful woman.
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   3. (Zool.) Any one of several species of very brilliant South
      American humming birds, having a very long and
      deeply-forked tail; as, the blue-tailed sylph (Cynanthus
      cyanurus).
      [1913 Webster]