From BiblePortal Wikipedia

Vine's Expository Dictionary of NT Words [1]

1: Ἀμετανόητος (Strong'S #279 — Adjective — ametanoetos — am-et-an-o'-ay-tos )

lit., "without change of mind" (a, negative, metanoeo, "to change one's mind," meta, signifying "change," nous, "the mind"), is used in  Romans 2:5 , "impenitent" (or "unrepentant"). Moulton and Milligan show from the papyri writings that the word is also used "in a Passive sense, 'not affected by change of mind,' like ametameletos in  Romans 11:29 ," "without repentance."

Webster's Dictionary [2]

(1): ( a.) Not penitent; not repenting of sin; not contrite; of a hard heart.

(2): ( n.) One who is not penitent.

King James Dictionary [3]

IMPEN'ITENT, a. Not penitent not repenting of sin not contrite obdurate of a hard heart.

They died Impenitent.

IMPEN'ITENT, n. One who does not repent a hardened sinner.