The term oblique refers to being neither parallel nor perpendicular.

The term is used to describe many geometric objects such as the ones below.

Oblique angle

An oblique angle is an angle that does not measure 90° or some multiple of 90°. If two intersecting lines are not perpendicular, oblique angles are formed. The lines are oblique lines.

Oblique triangles

An oblique triangle contains no interior angle that is a right angle. An oblique triangle can be further categorized as either an acute triangle or an obtuse triangle.

Acute triangleObtuse Triangle
Each angle has a measure less than 90°.An obtuse triangle contains one angle greater than 90°.

Oblique prisms

An oblique prism is a prism whose lateral faces are not perpendicular to its bases.

Oblique cylinder

Like the oblique prism, the sides of an oblique cylinder are not perpendicular to its circular bases.

Oblique pictorials

An oblique pictorial describes the result of drawing a representation of a 3D figure on a 2D plane, such as a piece of paper.

As an example, draw a cube on a piece of paper, as shown below. First, a square face is drawn as it would look head-on. Then, four parallel line segments are drawn at 45° from each vertex of the square, forming the other faces of the cube, and giving it a 3D view.