UNDERCOAT • FREE TRANSLATOR.ORG • Definition of Undercoat

... four-foot kin the cold north lands, it was necessary to clothe these little brethren of ours in a coat that should be absolutely warm, light, durable, of protective colour, thick in cold weather, thin in warm. Under these conditions she produced fur, with its densely woolly undercoat and its long, soft, shining outer coat, one for warmth, the other for wet and wear. Some northern animals can store up food in holes or in the fat of their bodies, so need not be out when the intensest cold is on the land. Some have to face the weather all ...

— Wild Animals at Home • Ernest Thompson Seton