A person 50 years old, or in his or her fifties.
Of or characteristic of a person in his or her fifties.
[From Latin quīnquāgēnārius, containing fifty, from quīnquāgēnī, fifty each, from quīnquāgintā, fifty; see penkwe in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.