Source : Webster's Revised Unabridged Dictionary (1913)

Iceberg \Ice"berg`\, n. [Prob. of Scand. origin; cf. Dan.
   iisbierg, Sw. isberg, properly, a mountain of ice. See {Ice},
   and {Berg}.]
   A large mass of ice, generally floating in the ocean.

   Note: Icebergs are large detached portions of glaciers, which
         in cold regions often project into the sea.

Source : WordNet®

iceberg
     n 1: a large mass of ice floating at sea; usually broken off of a
          polar glacier [syn: {berg}]
     2: lettuce with crisp tightly packed light-green leaves in a
        firm head; "iceberg is still the most popular lettuce"
        [syn: {crisphead lettuce}, {iceberg lettuce}]