As nouns the difference between summit and backshot
is that
summit is (countable) a peak; the top of a mountain while
backshot is (chiefly|sport).
As a verb summit
is (transitive|hiking|climbing|colloquial) to reach the summit of a mountain.
As an adjective backshot is
(of a water wheel) having the water introduced just behind the summit, combining the advantages of breastshot and overshot systems, since the full amount of the potential energy released by the falling water is harnessed as the water descends the back of the wheel.