"quinquagenarian"

quin·qua·ge·nar·i·an   (kwngkw-j-nâr-n)

n.

A person 50 years old, or in his or her fifties.

adj.

Of or characteristic of a person in his or her fifties.

---

[From Latin qunqugnrius, containing fifty, from qunqugn, fifty each, from qunqugint, fifty; see penk^we in Indo-European roots.]