Discover what perpendicular lines are, what they are not, how to draw them through clear definitions, easy-to-follow instructions, visuals, and a quick quiz. PERPENDICULAR definition: 1. at an angle of 90° to a horizontal line or surface: 2. at an angle of 90° to another line or…. Learn more. Perpendicular is also used as a noun: a perpendicular is a line which is perpendicular to a given line or plane. Perpendicularity is one particular instance of the more general mathematical concept of orthogonality; perpendicularity is the orthogonality of classical geometric objects.
