Nicking the line

Hitting a ball so that it comes as close as possible to landing outside the limits of a court, but actually, even if most of the ball has landed out, has had a tiny portion of it clip the line, which means the shot was good. It is the role of the linesman, peering along that line, to render decision, and it invariably subjects him/her to catcalls, whistles, and jeers from partisans in the stands, regardless of how far away they may be sitting, or at how poor an angle.