noun1. (in Britain 1981–90) a centre political party founded by ex-members of the Labour Party. It formed an alliance with the Liberal Party and continued in a reduced form after many members left to join the Social and Liberal Democratic Party in 1988
2. one of the two major political parties in Germany (formerly in West Germany), favouring gradual reform
3. any of the parties in many other countries similar to that of Germany
Social Democratic Party