ice floe

Etymology
From.

Noun

 * 1) Any type of sea ice not attached to land, drift ice.
 * 2) An ice dam (ice jam), a blockage of ice in a river starting with an ice floe in the river.
 * 3) An ice stream (ice flow), a type of fast moving glacier
 * 4) A flat mass of floating ice, smaller than an ice field.

Synonyms

 * ice float