/
sɪlf/
n.
   - an imaginary spirit of the air.
 - a slender woman or girl.
 - a mainly dark green and blue hummingbird with a long forked tail. 
[Genera Aglaiocercus and Neolesbia.]
 
Derivative
Etymology
C17: from mod. L. sylphes, sylphi and the Ger. pl. Sylphen, perh. based on L. sylvestris ‘of the woods’ + nympha ‘nymph’.