<p><strong>Verb</strong></p><ul><li>(used without object), hummed, hum·ming.</li><li>to make a low, continuous, droning sound.</li><li>to give forth an indistinct sound of mingled voices or noises.</li><li>to utter an indistinct sound in hesitation, embarrassment, dissatisfaction, etc.; hem.</li><li>to sing with closed lips, without articulating words.</li><li>to be in a state of busy activity: The household hummed in preparation for the wedding.</li><li>Synonyms: buzz, bustle.</li><li>British Slang: to have a bad odor, as of stale perspiration.</li></ul><p><strong>Noun</strong></p><ul><li>the act or sound of humming; an inarticulate or indistinct murmur; hem.</li><li>Audio: an unwanted low-frequency sound caused by power-line frequencies in any audio component.</li></ul><p><strong>Interjection</strong></p><ul><li>(an inarticulate sound uttered in contemplation, hesitation, dissatisfaction, doubt, etc.)</li></ul>