1.[I,T]（使）变硬，（使）坚固，（使）硬化
2. 不及物动词：变得更坚定，变得冷酷无情
3. 及物动词：使变得坚强，使更有忍耐力 词形变化
- 时态 hardened，hardened，hardening，hardens
- become hard or harder
- cause to accept or become hardened to; habituate
- harden by reheating and cooling in oil
- make hard or harder
- make fit