Rous sarcoman. A sarcoma produced in poultry by a retrovirus.[After Francis Peyton Rous (1879-1970), American pathologist and Nobel laureate.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.Rous? sarco`ma (ra?s) n. a malignant tumor occurring in the connective tissue of poultry, caused by a retrovirus. [after Francis PeytonRous(1879?1970), U.S. pathologist, who described it in 1910] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.