The Collaborative International Dictionary of English v.0.48:

Floe \Floe\ (fl[=o]), n. [Cf. Dan. flag af iis, iisflage, Sw.
   flaga, flake, isflaga, isflake. See Flag a flat stone.]
   A low, flat mass of floating ice.
   [1913 Webster]

   Floe rat (Zool.), a seal (Phoca f[oe]tida).
      [1913 Webster]

WordNet (r) 3.0 (2006):

floe
    n 1: a flat mass of ice (smaller than an ice field) floating at
         sea [syn: ice floe, floe]

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "floe":
   Dry Ice, berg, calf, cryosphere, firn, frazil, frozen water,
   glaciation, glacier, glacieret, glaze, glazed frost, granular snow,
   ground ice, growler, ice, ice banner, ice barrier, ice belt,
   ice cave, ice cubes, ice dike, ice field, ice floe, ice foot,
   ice front, ice island, ice needle, ice pack, ice pinnacle,
   ice raft, ice sheet, iceberg, icefall, icequake, icicle, jokul,
   lolly, neve, nieve penitente, pack ice, serac, shelf ice, sleet,
   slob, sludge, snow ice, snowberg