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.”
The last stage of life; old age.
Senectitude comes from the Medieval Latin noun senectitūdō meaning “old age,” which in turn comes from Classical Latin senectūs, a derivative of the noun senex meaning “old man.” Senectitude entered English in the late 1700s, more precisely, in 1796 in Jonathan Swift’s Gulliver’s Travels