backbencher

noun

1. A Member of Parliament who does not have cabinet rank, and who therefore sits on one of the backbenches or in one of the back rows of the legislature.
2. A student who does not perform well, especially one who sits at the back of the classroom.

   “Classmates naturally turn to look at the backbencher, who must acknowledge his presence, with some embarrassment.”

   “The teacher also gets an idea of the "backbenchers" or the slow students since he can see which desk is still to send an answer.”

   “When I was in a primary school, I was a backbencher student.”

3. A member of a team who does not usually play, but who is held in reserve.

   “During 1994, the national team players were away for a game in January and again during the season-ending league championship tournament in April. The “backbenchers” won all these games.”

   “The plucky backbencher began his life in hockey as a player, breaking into the professional game with the Pacific Coast Hockey Association's Portland Rosebuds in 1916– 17, but turned amateur again the following season.”

   “By the second scrimmage of the season he was a backbencher, suspended from the game for disciplinary reasons.”

4. (broadly)Someone who does not play an active role in a process.

   “As we stated in previous chapters, counselors and other student support personnel have been backbenchers in the ongoing drama of school reform.”

   “Mayorga was no backbencher in the dirty war. He had been chief of the naval base in Trelew in 1972, when one of the first massacres took place.”

   “But, Jack was a backbencher in the committee. His main function was to keep an eye on the theatre's income.”