To sing a wordless tune with closed lips

• To express a melody by humming

To make a low continuous sound, like a machine

• To buzz or drone like insects
• To be briskly active or lively, of a place

A low, steady, continuous sound

• A tune produced by humming
• Lively activity with background noise

Used to show thinking, hesitation, or doubt

An instance of the interjection "um" in transcription

A persistent, unexplained low-frequency humming heard by some people

To smell unpleasant; to reek

An unpleasant odor