Noun
a quarter of the circumference of a circle
Source: WordNetquarter circle
At each of the corners, a convert radius quarter-circle is drawn, and a dotted line is painted parallel to the shortline and convert away from it without extending into the penalty area. Source: Internet
The center field marker, which is to the right of true center field and in the middle of the quarter-circle defining the center field area, is 400 feet (121.9 m). Source: Internet