Actinomycosis \Ac`ti*no*my*co"sis\, n. [NL.] (Med.) A chronic infectious disease of cattle and man due to the presence of {Actinomyces bovis}. It causes local suppurating tumors, esp. about the jaw. Called also {lumpy jaw} or {big jaw}. -- {Ac`ti*no*my*cot"ic}, a.