[f. TOUCH sb. or v. + LINE sb.2]
† 1. Geom. A straight line that touches a curve; a tangent. Obs. (Orig. two words.)
1551. Recorde, Pathw. Knowl., I. Defin., A touche lyne, is a line that runneth a long by the edge of a circle, onely touching it, but doth not crosse the circumference of it.
1593. Fale, Dialling, 7. Which shall be called the touch line or line of Contingence.
1675. Collins, in Rigaud, Corr. Sci. Men (1841), I. 217. If you conceive a chord line to join R, T, and a touch-line to be drawn at either of those.
2. (touch line.) A line in a diagram representing the touch of the counter of a ship: see TOUCH sb. 23.
1797. Encycl. Brit. (ed. 3), XVII. 392/1. Take the round up of the upper counter from the dimensions, and set it below the touch at the middle, and with a pencil draw a level line; take also the round aft, and set it forward from the touch on the touch line, and square it down to the pencil line.
3. Football. The boundary line on each side of the field of play, extending from goal-line to goal-line: cf. TOUCH sb. 12.
1868. Boy’s own Bk., 132 [Diagram of football ground]. The goals at either end;… the goal lines;… touch, the touch lines.
1889. Pauline, VIII. 38. The kick, which was very near the touch-line, was not successful.
1895. Outing (U.S.), XXVII. 247/2. The Canadian football field…. Along the edges, from one end to another, run the ‘touch lines,’ and when the ball goes over these it is not in play.
