An oblique angle is an angle that is not a right angle or any multiple of a right angle. This means that the sides forming the angle cannot be perpendicular.
In geometry, acute angles measure between 0 and 90 degrees, and obtuse angles measure between 90 and 180 degrees. Both acute angles and obtuse angles are oblique angles.
The term oblique can also be used to describe plane figures and space figures.
Oblique plane figures
An oblique triangle is a triangle that is not a right triangle.
When the intersection of two planes forms an oblique angle, the planes are called oblique planes.
Oblique space figures
The rectangular prism shown below is oblique since its bases are not directly in line with each other.
Both the cone and the pyramid shown are also oblique since their apexes are not directly in line with the center of their bases.