Pronunciation: (big'hed', -hed"),[key] —n. 1. Informal.an excessive estimate of one's importance; conceit.
2. Vet. Pathol. a. an inflammatory swelling of the tissues of the head of sheep, caused by the anaerobic bacillus Clostridium novyi. b. enlargement of the head and jawbones of horses resulting from nutritional hyperthyroidism.