a former group of five states in the Malay Peninsula, under indirect British control and forming a part of the former Federation of Malaya: now part of the federation of Malaysia. 24,347 sq. mi. (63,059 sq. km).
British Dictionary definitions for un federated malay states
Unfederated Malay States
a former group of native states in the Malay Peninsula that became British protectorates between 1885 and 1909. All except Brunei joined the Malayan Union (later Federation of Malaya) in 1946. Brunei joined the Federation of Malaysia in 1963 but later became an independent nation