At an angle of 90° to a given line, plane, or surface or to the ground.
Late Middle English (as an adverb meaning ‘at right angles’): via Old French from Latin perpendicularis, from perpendiculum ‘plumb line’, from per- ‘through’ + pendere ‘to hang’.
“The lamp post sat perpendicular to the street.”
Originally: a bald head; a bald-headed person. In later use also: a pitiable, lowly, or foolish person; a shabby or unkempt person. Frequently used without article, as though a proper name.
Early 16th century; earliest use found in John Skelton (c1460–1529), poet. In some forms apparently partly from pilled + garlic and partly from peeled + garlic; in some forms apparently partly from pill + garlic and partly from peel + garlic.