Meaning of quinquagenarian

quin•qua•ge•nar•i•an

Pronunciation: (kwing"kwu-ju-nâr'ē-un, kwin"-), [key]
— adj.
  1. 50 years of age.
  2. between the ages of 50 and 60.
—n.
  1. a person who is 50 years old or whose age is between 50 and 60.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.