I. adjective
Etymology: Middle English hardned, from past participle of hardnen to harden
1. : made hard or harder
hardened brass
hardened roads
2.
a. : grown unfeeling or callous
hardened as I am, I felt a thrill of horror — Allen Upward
b. : confirmed , inveterate , veteran
many of the findings will hardly appeal except to hardened Johnsonians — Times Literary Supplement
hardened fishermen protested — L.F.Ranlett
a commercial or otherwise hardened traveler — W.C.Brownell
specifically : confirmed in error or vice
a hardened little reprobate — W.M.Thackeray
a hardened heretic
hardened criminals
c. : grown or become inured or steeled
the duty was easy for a hardened horseman — S.H.Adams
hardened fighting men
II. adjective
: protected from possible danger from blast or heat by means of concrete or earth or by being situated underground
a hardened missile launching site
a hardened missile