Right-angled; having one or more angles of ninety degrees.

DRAINAGE: A system of streams in which each straight segment of each stream takes one of two characteristic perpendicular directions, usually following sets of joints.

having four right angles; "a rectangular figure twice as long as it is wide"

having a set of mutually perpendicular axes; meeting at right angles; "wind and sea may displace the ship's center of gravity along three orthogonal axes"; "a rectangular Cartesian coordinate system"

A particular shape of a container which has right angles with adjacent sides of unequal dimensions.

Having four sides, more or less at right angles, and with one dimension obviously longer than the other; sometimes used specifically for a rectangular shape that is longer than broad (compare with quadrate and quadrangular).