A fortified strip or boundary usually protecting a military position.
The outer limits of an area. See synonyms at circumference.
An instrument for determining the extent and shape of the field of vision.
The length of such a boundary.
The sum of the distance of all the lengths of the sides of an object.
A simple fence made from wooden pickets, connected by horizontal bars.
A series of spaced perpendicular striations that occasionally occur in aurorae.