The Collaborative International Dictionary of English v.0.48:

Siren \Si"ren\, n. [L., fr. Gr. ???: cf. F. sir[`e]ne.]
   1. (Class. Myth.) One of three sea nymphs, -- or, according
      to some writers, of two, -- said to frequent an island
      near the coast of Italy, and to sing with such sweetness
      that they lured mariners to destruction.
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            Next where the sirens dwell you plow the seas;
            Their song is death, and makes destruction please.
                                                  --Pope.
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   2. An enticing, dangerous woman. --Shak.
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   3. Something which is insidious or deceptive.
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            Consumption is a siren.               --W. Irving.
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   4. A mermaid. [Obs.] --Shak.
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   5. (Zool.) Any long, slender amphibian of the genus Siren
      or family Sirenidae, destitute of hind legs and pelvis,
      and having permanent external gills as well as lungs. They
      inhabit the swamps, lagoons, and ditches of the Southern
      United States. The more common species (Siren lacertina)
      is dull lead-gray in color, and becames two feet long.
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   6. [F. sir[`e]ne, properly, a siren in sense 1.] (Acoustics)
      An instrument for producing musical tones and for
      ascertaining the number of sound waves or vibrations per
      second which produce a note of a given pitch. The sounds
      are produced by a perforated rotating disk or disks. A
      form with two disks operated by steam or highly compressed
      air is used sounding an alarm to vessels in fog. [Written
      also sirene, and syren.]
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The Collaborative International Dictionary of English v.0.48:

Syren \Sy"ren\, n.
   See Siren. [R.]
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