archipelago

from WordNet (r) 3.0 (2006)

archipelago
    n 1: a group of many islands in a large body of water

from The Collaborative International Dictionary of English v.0.48

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}.]
   [1913 Webster]
   1. The Grecian Archipelago, or [AE]gean Sea, separating
      Greece from Asia Minor. It is studded with a vast number
      of small islands.
      [1913 Webster]

   2. Hence: Any sea or broad sheet of water interspersed with
      many islands or with a group of islands.
      [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

20 Moby Thesaurus words for "archipelago":
      ait, atoll, bar, cay, continental island, coral head, coral island,
      coral reef, holm, insularity, island, island group, islandology,
      isle, islet, key, oceanic island, reef, sandbank, sandbar