<p><strong>Verb</strong></p><ul><li>to make flat.</li><li>to knock down: The boxer flattened his opponent in the second round.</li></ul><p><strong>Noun</strong></p><ul><li>to become flat.</li></ul><p><strong>Verb Phrase</strong></p><ul><li>to fly into a horizontal position, as after a dive.</li></ul>