<p><strong>Verb (used with object)</strong></p><ul><li>to make stiff.</li></ul><p><strong>Verb (used without object)</strong></p><ul><li>to become stiff.</li><li>to become suddenly tense, rigid, or taut, as in bracing oneself for or drawing back from shock, fear, or displeasure: He stiffened, expecting to hear the worst.</li></ul>