ice floe

noun
1.
a large flat mass of floating ice.
2.
floe (def 1).
Origin
1810-20
British Dictionary definitions for ice floe

ice floe

noun
1.
a sheet of ice, of variable size, floating in the sea See also ice field (sense 1)
ice floe in Science
ice floe  
A large, flat expanse of floating ice smaller than a marine ice field.