That's an Eeno.
Eeno are mounds of snow that live in cold environments and throw snowballs at Link when he is within range. There are large ones as well, which will split into three regular ones when attacked. If left alone for long enough, however, they will reform into a large Eeno again.
They are weak enemies, and easily defeated. Their attacks can easily be blocked by Link's Shield. Fire, specifically Fire Arrows, defeats them instantly, regardless of size.