From WordNet (r) 3.0 (2006) [wn]:
igloo
n 1: an Eskimo hut; usually built of blocks (of sod or snow) in
the shape of a dome [syn: igloo, iglu]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Igloo \Ig"loo\, n.
1. An Eskimo snow house.
[1913 Webster]
2. (Zool.) A cavity, or excavation, made in the snow by a
seal, over its breathing hole in the ice.
[1913 Webster]