<p><strong>Verb (used without object)</strong></p><ul><li>to move with a sinuous or wavelike motion; display a smooth rising-and-falling or side-to-side alternation of movement: The flag undulates in the breeze.</li><li>to have a wavy form or surface; bend with successive curves in alternate directions.</li><li>(of a sound) to rise and fall in pitch: the wail of a siren undulating in the distance.</li></ul><p><strong>Verb (used with object)</strong></p><ul><li>to cause to move in waves.</li><li>to give a wavy form to.</li></ul><p><strong>Adjective</strong></p><ul><li>also undulated.</li><li>having a wavelike or rippled form, surface, edge, etc.; wavy.</li></ul>