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.