rous sarcoma noun alsorous' sarcomaorrous's sarcoma\ˈrau̇s(ə̇z)-\ Usage: usually capitalized R Etymology: after F. Peyton Rous b1879 American physician : a readily transplantable malignant spindle-cell sarcoma of chickens that is transmissible by cell-free filtrate and so is regarded as due to a specific carcinogenic virus