Source : Webster's Revised Unabridged Dictionary (1913)

Delta \Del"ta\, n.; pl. {Deltas}. [Gr. de`lta, the name of the
   fourth letter of the Greek alphabet (the capital form of
   which is [Delta], Eng. D), from the Ph[oe]nician name of the
   corresponding letter. The Greeks called the alluvial deposit
   at the mouth of the Nile, from its shape, the Delta of the
   Nile.]
   A tract of land shaped like the letter delta ([Delta]),
   especially when the land is alluvial and inclosed between two
   or more mouths of a river; as, the delta of the Ganges, of
   the Nile, or of the Mississippi.