mandamus /mænˈdeɪməs/noun 1verb 1forms 3 noun1 •A common law prerogative writ that compels a court or government officer to perform mandatory or purely ministerial duties correctly.The lord is compellable by mandamus to admit the surrenderee, that is, the person to whose use the surrender is made. — 1876 verb1 •To serve a writ of this kind upon. formsmandamused · mandamusing · mandamuses