A left-of-centre political party formed to represent the interests of ordinary working people, in particular a major British party that since the Second World War has been in power 1945–51, 1964–70, 1974–9, and 1997–2010. Arising from the trade union movement at the end of the 19th century, it replaced the Liberals as the country's second party after the First World War.
Definition of Labour Party in US English:
Labour Party
proper noun
A major left-of-center British party that since World War II has been in power 1945–51, 1964–70, 1974–79, and 1997–2010. Arising from the trade union movement at the end of the 19th century, it replaced the Liberals as the country's second party after World War I.