1. A disease of horses and other domestic animals, often occurring after castration, usually caused by Staphylococcus aureus and characterized by the formation of granulomatous masses (chronic inflammatory lesions characterised by large numbers of cells).
2. A chronic granulomatous condition of horses, cattle, swine, and people; usually involving the skin but occasionally also the viscera, and characterised by granules in the pus, consisting of masses of bacteria, generally staphylococci but sometimes other types, surrounded by a hyaline capsule which sometimes exhibits clublike bodies around its periphery.

The anatomic structure of the lesion resembles that of actinomycosis and mycetoma (chronic infection involving the feet).