What does "lobster" mean?

Lobster: 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 (Zoöl.), the caterpillar of a European bombycid moth (Stauropus fagi); -- so called from its form. Lobster louse (Zoöl.), a copepod crustacean (Nicothoë astaci) parasitic on the gills of the European lobster.