<p><strong>Verb (used with object)</strong></p><ul><li>to make hard or harder: to harden steel</li><li>to make pitiless or unfeeling: to harden one's heart</li><li>to make rigid or unyielding; stiffen: The rigors of poverty hardened his personality</li><li>to strengthen or confirm, especially with reference to character, intentions, feelings, etc.; reinforce</li></ul><p><strong>Synonyms</strong></p><ul><li>ossify</li><li>petrify</li><li>indurate</li><li>solidify</li><li>nerve</li><li>brace</li><li>steel</li><li>fortify</li></ul><p><strong>Antonyms</strong></p><ul><li>soften</li><li>weaken</li></ul><p><strong>Verb (used without object)</strong></p><ul><li>to become hard or harder</li><li>to become pitiless or unfeeling</li><li>to become rigid or unyielding; stiffen: His personality hardened over the years</li><li>to become confirmed or strengthened: His resistance hardened</li><li>to become inured or toughened: The troops hardened under constant fire</li></ul><p><strong>Commerce</strong></p><ul><li>(of a market, prices, etc.) to cease to fluctuate; firm: When the speculators withdrew from the market, the prices hardened</li><li>to rise higher.</li></ul>