Source : Webster's Revised Unabridged Dictionary (1913)

Archipelago \Ar`chi*pel"a*go\, n.; pl. {-goes} or {-gos}. [It.
   arcipelago, properly, chief sea; Gr. pref ? + ? sea, perh.
   akin to ? blow, and expressing the beating of the waves. See
   {Plague}.]
   1. The Grecian Archipelago, or [AE]gean Sea, separating
      Greece from Asia Minor. It is studded with a vast number
      of small islands.

   2. Hence: Any sea or broad sheet of water interspersed with
      many islands or with a group of islands.

Source : WordNet®

archipelago
     n : a group of many islands in a large body of water
     [also: {archipelagoes} (pl)]