con·gres·sion·al. adj. 1. Of or relating to a congress: a congressional convention. 2. Relating to or working in the office of a member or members of a congress: a congressional aide. n. A member of a congress.on·gres·sion·al. adj. 1. Of or relating to a congress: a congressional convention. 2. Relating to or working in the office of a member or members of a congress: a congressional aide. n. A member of a congress.