Definition of "clinching"

‘Yes,’ said Dick, with such a clinching period at the end that it seemed he was never going to add another word.

1872, [Thomas Hardy], “VIII. Dick Meets His Father”, in Under the Greenwood Tree: A Rural Painting of the Dutch School, volume II, London: Tinsley Brothers, part II, page 16

There were no dreams,No phantoms in her future any more:One clinching revelation of what wasOne by-flash of irrevocable chance,Had acridly but honestly foretoldThe mystical fulfilment of a lifeThat might have once … But that was all gone by

1921, Edwin Arlington Robinson, “Imogen”, in Collected Poems‎, lines 113–119

He shocked his hearers by urging them not to fast during Ramadan, which begins Feb. 29. As a clinching argument, Bourguiba recalled that even Mohammed, when inconveniently overtaken by Ramadan on his march to Mecca, counseled his soldiers: “Break the fast, and you will be stronger to confront the enemy.”

1960 February 22, “Breaking the Fast”, in Time

Though there are no kissings and clinchings, […]

1937, Motion Picture Herald, volume 127, numbers 1-6, page 42

Only six weeks into the season, the top-ranked Bulldogs were undefeated at 60, but more important to Louisiana Tech was one of the earliest clinchings of a conference title in the annals of college football.

2015, George Becnel, The Southland Conference: Small College Football, Big Dreams

This “clinching” can distort the tape by causing a series of creases or folds in the surface and may produce read errors.

1985, Alvin C. Larson, Computer Operator (AFSC 51150), page 87

Computer magnetic tape is designed primarily for its storage capacity, speed, and capacity to be repeatedly erased and written over. […] Bad binder can cause holes in the oxide, loose particles, or clinching of tape.

1987, Conservation Administration News, numbers 28-35, page 29