hardened

adjective

Completely lacking in compassion: callous, cold-blooded, cold-hearted, compassionless, hard, hard-boiled, hardhearted, heartless, obdurate, stonyhearted, unfeeling. See attitude/good attitude/bad attitude/neutral attitude.

adj. 1. having become or been made hard or harder: hardened steel.

2. strengthened or made secure against attack, especially by nuclear weapons: the silos are hardened against air attack.

3. experienced in a particular job or activity and therefore not easily upset by its more unpleasant aspects: a battle-hardened veteran.

See the Introduction, Abbreviations and Pronunciation for further details.

The adjective has 4 meanings:

Meaning #1: used of persons; emotionally hardened
  Synonyms: case-hardened, hard-boiled

Meaning #2: made hard or flexible or resilient especially by heat treatment
  Synonyms: tempered, treated, toughened

Meaning #3: made tough by habitual exposure
  Synonyms: enured, inured

Meaning #4: converted to solid form (as concrete)
  Synonym: set