mandatory UK /ˈmæn.də.t(ə)ɹi/US /ˈmæn.dəˌtɔɹ.i/adjective 2noun 2forms 3 adjective2 •obligatory; required or commanded by authority.Attendance at a school is usually mandatory for children. •Of, being or relating to a mandate. noun2 •A sign or line that require the path of the disc to be above, below or to one side of it. •(old-fashioned, rare) A person, organisation or state who receives a mandate; a mandatary. formsmandatories · more mandatory · most mandatory