me·du·sa /mɪˈdusə, ˈdju, zə/
 水母


 Me·du·sa n.
 1. Class. Myth. The Gorgon; or one of the Gorgons whose hair was changed into serpents, after which all who looked upon her were turned into stone.
 2. [pl. Medusae ] Zool. Any free swimming acaleph; a jellyfish.
 Note: ☞ The larger medusae belong to the Discophora, and are sometimes called covered-eyed medusae; others, known as naked-eyed medusae, belong to the Hydroidea, and are usually developed by budding from hydroids. See Discophora, Hydroidea, and Hydromedusa.
 Medusa bud Zool., one of the buds of a hydroid, destined to develop into a gonophore or medusa. See Athecata, and Gonotheca.
 Medusa's head. (a) Zool. An astrophyton. (b) Astron. A cluster of stars in the constellation Perseus.  It contains the bright star Algol.

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 Medusa
      n 1: (Greek mythology) a woman transformed into a Gorgon by
           Athena; she was slain by Perseus
      2: any of numerous usually marine and free-swimming
         coelenterates that constitute the sexually reproductive
         forms of hydrozoans and scyphozoans [syn: jellyfish, medusan]
      3: one of two forms that coelenterates take: is the
         free-swimming sexual stage in the life cycle of a
         coelenterate and has a gelatinous umbrella-shaped body and
         tentacles