perimeter

A closed line bounding a plane area.

The length of such a line.

The outer limits of an area. synonym: circumference.

A defended boundary protecting a military position.

The three-point line.

The circumference, border, or outer boundary of a superficial figure; also, the measure of this boundary.

An instrument for determining the visual power of different parts of the retina and plotting areas of distinct vision.

The outer boundary of a body or figure, or the sum of all the sides.

An instrument for determining the extent and shape of the field of vision.