n :  either of two forms of a disease esp. of chickens and turkeys that is caused by a DNA virus and is characterized by head lesions  a  :  a cutaneous form marked by pustules, warty growths, and scabs esp. on skin that lacks feathers - called also sorehead   b  :  a more serious form occurring as cheesy lesions of the mucous membranes of the mouth, throat, and eyes that sometimes coalesce into a false membrane .
 
 
 
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