Noun
brown adipose tissue (countable and uncountable, plural brown adipose tissues)
(anatomy, physiology) One of the two types of adipose tissue present in many newborn or hibernating mammals which primarily serves to generate body heat, and which contains several small vacuoles and a relatively high number of mitochondria and capillaries.
Brown adipose tissue is found in mammals, and is at its highest levels in early life and in hibernating animals. Source: Internet