parliamentary UK /ˌpɑːləˈmɛnt(ə)ɹi/US /ˌpɑɹləˈmɛnt(ə)ɹi/adjective 3noun 1forms 1 adjective3 •Of, relating to, or enacted by a parliament.Parliamentary procedures are sometimes slow. •Having the supreme executive and legislative power resting with a cabinet of ministers chosen from, and responsible to a parliament.The UK is a parliamentary democracy. •(UK, historical) Of a class of train which, by an act of parliament, ran both ways along a line, at least once each day, at the rate of one penny per mile. noun1 •(UK, historical) A parliamentary train. formsparliamentaries