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心    如    铁    石    心象铁石一样坚硬。比喻心肠硬或意志十分坚决。 贬义>

心像铁石一样坚硬

Keep one's heart as hard as the nether millstone

心如刀锯    心同止水    心长发短    心细如发    心胆俱裂