Source : Webster's Revised Unabridged Dictionary (1913)

Lobster \Lob"ster\, n. [AS. loppestre, lopystre prob., corrupted
   fr. L. locusta a marine shellfish, a kind of lobster, a
   locust. Cf. {Locust}.] (Zo["o]l.)
   Any large macrurous crustacean used as food, esp. those of
   the genus {Homarus}; as the American lobster ({H.
   Americanus}), and the European lobster ({H. vulgaris}). The
   Norwegian lobster ({Nephrops Norvegicus}) is similar in form.
   All these have a pair of large unequal claws. The spiny
   lobsters of more southern waters, belonging to {Palinurus},
   {Panulirus}, and allied genera, have no large claws. The
   fresh-water crayfishes are sometimes called lobsters.

   {Lobster caterpillar} (Zo["o]l.), the caterpillar of a
      European bombycid moth ({Stauropus fagi}); -- so called
      from its form.

   {Lobster louse} (Zo["o]l.), a copepod crustacean
      ({Nicotho["e] astaci}) parasitic on the gills of the
      European lobster.