Definitions for "backbencher"
a member of the House of Commons of Great Britain who is not a party leader.
(Local government) A Councillor who is not a member of a Council's decision-making Executive. Backbenchers vote on their local authority's policy framework and sit on scrutiny committees, as well representing their constituents.
A Member of Parliament who is not a Minister and holds no special office (such as President or Speaker); the name is used because such Members sit on the benches at the back of the House.
a Member who holds no official position in government or in his or her party
an MP who has no office in government and is not and is not an official party spokesperson)