<p><strong>Verb (used without object):</strong></p><ul><li>to decrease in strength, intensity, etc.</li><li>to fall away, as in quality; degenerate.</li><li>to decline in power, importance, prosperity, etc.</li><li>to draw to a close; approach an end.</li><li>(of the moon) to decrease periodically in the extent of its illuminated portion after the full moon.</li></ul><p><strong>Noun:</strong></p><ul><li>a gradual decrease or decline in strength, intensity, power, etc.</li><li>the drawing to a close of life, an era, a period, etc.</li><li>the waning of the moon.</li><li>a period of waning.</li><li>a defect in a plank or board characterized by bark or insufficient wood at a corner or along an edge, due to the curvature of the log.</li></ul>