Origin: 1300-1400 Old French perpendiculer, from Latin, from perpendiculum plumb line, from pendere to hang
1math, geometry if one line is perpendicular to another line, they form an angle of 90 degrees where they cross: perpendicular linesperpendicular to First Street is perpendicular to Main Street.2not leaning to one side or the other but exactly uprightSYN vertical: a perpendicular pole3Perpendicular in the style of 14th- and 15th-century English churches which are decorated with straight upright lines—perpendicularly adverb