seditionary adjective 1noun 1forms 3 adjective1 •Constituting or relating to sedition. noun1 •An inciter or promoter of sedition; a seditionist.They believed the Americans to be traitors and seditionaries, ungrateful for the benefits that had accrued to them and unwilling to pay a fair contribution to the expenses of empire. — 2016 formsseditionaries · more seditionary · most seditionary