Palmerstonian UK /ˌpɑːməˈstəʊ.ni.ən/US /ˌpɑmɚˈstoʊ.ni.ən/ adjective1 •Of or pertaining to Henry John Temple, 3rd Viscount Palmerston (1784–1865), British prime minister. formsmore Palmerstonian · most Palmerstonian