The Collaborative International Dictionary of English v.0.48:

Carob \Car"ob\, n. [Cf. F. caroube fruit of the carob tree, Sp.
   garrobo, al-garrobo, carob tree, fr. Ar. kharr[=u]b, Per.
   Kharn[=u]b. Cf. Clgaroba.]
   1. (Bot.) An evergreen leguminous tree (Ceratania Siliqua)
      found in the countries bordering the Mediterranean; the
      St. John's bread; -- called also carob tree.
      [1913 Webster]

   2. One of the long, sweet, succulent, pods of the carob tree,
      which are used as food for animals and sometimes eaten by
      man; -- called also St. John's bread, carob bean, and
      algaroba bean.
      [1913 Webster]

WordNet (r) 3.0 (2006):

carob
    n 1: long pod containing small beans and sweetish edible pulp;
         used as animal feed and source of a chocolate substitute
         [syn: carob, carob bean, algarroba bean, algarroba,
         locust bean, locust pod]
    2: evergreen Mediterranean tree with edible pods; the biblical
       carob [syn: carob, carob tree, carob bean tree,
       algarroba, Ceratonia siliqua]
    3: powder from the ground seeds and pods of the carob tree; used
       as a chocolate substitute [syn: carob, carob powder,
       Saint-John's-bread]