'Locust bean' definitions:

Definition of 'locust bean'

noun

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]

From: GCIDE

Locust \Lo"cust\, n. [L. locusta locust, grasshopper. Cf. Lobster.]
1. (Zool.) Any one of numerous species of long-winged, migratory, orthopterous insects, of the family Acridid[ae], allied to the grasshoppers; esp., ({Edipoda migratoria}, syn. Pachytylus migratoria, and {Acridium perigrinum}, of Southern Europe, Asia, and Africa. In the United States the related species with similar habits are usually called grasshoppers. See Grasshopper. [1913 Webster]
Note: These insects are at times so numerous in Africa and the south of Asia as to devour every green thing; and when they migrate, they fly in an immense cloud. In the United States the harvest flies are improperly called locusts. See Cicada. [1913 Webster]
Locust beetle (Zool.), a longicorn beetle ({Cyllene robini[ae]}), which, in the larval state, bores holes in the wood of the locust tree. Its color is brownish black, barred with yellow. Called also locust borer.
Locust bird (Zool.) the rose-colored starling or pastor of India. See Pastor.
Locust hunter (Zool.), an African bird; the beefeater. [1913 Webster]
2. [Etymol. uncertain.] (Bot.) The locust tree. See {Locust Tree} (definition, note, and phrases). [1913 Webster]
Locust bean (Bot.), a commercial name for the sweet pod of the carob tree. [1913 Webster]