[in.flu.en.za] n [It, lit., influence, fr. ML influentia; fr. the belief that epidemics were due to the influence of the stars] (1743) 1: an acute highly contagious virus disease caused by various strains of a myxovirus (family Orthomyxoviridae) and characterized by sudden onset, fever, prostration, severe aches and pains, and progressive inflammation of the respiratory mucous membrane; broadly: a human respiratory infection of undetermined cause
2: any of numerous febrile usu. virus diseases of domestic animals marked by respiratory symptoms, inflammation of mucous membranes, and often systemic involvement -- in.flu.en.zal adj