The term 'REALLY COLD' can be described by a variety of words, including POLAR (5 letters), ARCTIC (6 letters), ICY (3 letters), BELOWO (6 letters), and BELOWZERO (9 letters). POLAR refers to the area around the North and South Poles, which is known for its extreme cold temperatures. ARCTIC is another word for the same region, while ICY implies a temperature that is very cold. BELOWO and BELOWZERO both refer to temperatures that are even colder than ICY.