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. 2. Fig.: A slender, graceful woman. 3. (Zo["o]l.) 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}).