Antonyms of adj rectangular

2 senses of rectangular

Sense 1
rectangular -- (having four right angles; "a rectangular figure twice as long as it is wide")

INDIRECT (VIA angular) -> rounded -- (curving and somewhat round in shape rather than jagged; "low rounded hills"; "rounded shoulders")

Sense 2
orthogonal, rectangular -- (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")

INDIRECT (VIA parallel, perpendicular) -> oblique -- (slanting or inclined in direction or course or position--neither parallel nor perpendicular nor right-angled; "the oblique rays of the winter sun"; "acute and obtuse angles are oblique angles"; "the axis of an oblique cone is not perpendicular to its base")
INDIRECT (VIA perpendicular, oblique) -> parallel -- (being everywhere equidistant and not intersecting; "parallel lines never converge"; "concentric circles are parallel"; "dancers in two parallel rows")

Similarity of adj rectangular

2 senses of rectangular

Sense 1
rectangular -- (having four right angles; "a rectangular figure twice as long as it is wide")
       => angular (vs. rounded), angulate -- (having angles or an angular shape)

Sense 2
orthogonal, rectangular -- (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")
       => perpendicular (vs. oblique) (vs. parallel) -- (intersecting at or forming right angles; "the axes are perpendicular to each other")