dis ‧ ci ‧ pli ‧ nar ‧ i ‧ an /ˌdɪsəpləˈneəriən, ˌdɪsɪpləˈneəriən $ -ˈner-/ BrE AmE noun [countable]
[ Word Family: noun : ↑ disciplinarian , ↑ discipline ; adjective : ↑ disciplinary , ↑ disciplined ≠ UNDISCIPLINED ; verb : ↑ discipline ]
someone who believes people should obey orders and rules, and who makes them do this:
Dad was a strict disciplinarian.