<p><strong>Adjective</strong></p><ul><li>Having a space or cavity inside; not solid; empty: a hollow sphere.</li><li>Having a depression or concavity: a hollow surface.</li><li>Sunken, as the cheeks or eyes.</li><li>(of sound) Not resonant; dull, muffled, or deep: a hollow voice.</li><li>Without real or significant worth; meaningless: a hollow victory.</li><li>Hungry; having an empty feeling: I feel absolutely hollow, so let's eat.</li></ul><p><strong>Noun</strong></p><ul><li>An empty space within anything; a hole, depression, or cavity.</li><li>A valley: They took the sheep to graze in the hollow.</li><li>Foundry: A concavity connecting two surfaces otherwise intersecting at an obtuse angle.</li></ul><p><strong>Verb</strong></p><ul><li>(used with object) To make hollow (often followed by out): to hollow out a log.</li><li>To form by making something hollow (often followed by out): to hollow a place in the sand; boats hollowed out of logs.</li><li>(used without object) To become hollow.</li></ul><p><strong>Adverb</strong></p><ul><li>In a hollow manner: The politician's accusations rang hollow.</li></ul>