Webster’s Revised Unabridged Dictionary · 1913
Backset
Back′set′ (-sĕt′), n. [Back, adv. + set.] 1. A check; a relapse; a discouragement; a setback.
2. Whatever is thrown back in its course, as water.
Slackwater, or the backset caused by the overflow. Harper's Mag.
Back′set′, v. t. To plow again, in the fall; — said of prairie land broken up in the spring. [Western U.S.]