To thrum means to make a low, steady, continuous sound, like the hum of a motor or the vibration of guitar strings. When an engine thrums, it produces that deep, rhythmic buzz that you can sometimes feel in your chest. A harp's strings thrum softly when plucked. A cat purring contentedly on your lap is thrumming in its own way.

The word captures both sound and vibration. Picture sitting in a car at a stoplight: the engine isn't roaring or rattling, it's just thrumming along steadily, almost like a heartbeat. A beehive thrums with the sound of thousands of wings beating. A guitar leaning against an amplifier might thrum from the vibrations of other instruments.

People also use thrum as a noun for a low, steady sound or vibration, like “the thrum of traffic” or “the thrum of machinery.” The word suggests something constant and rhythmic rather than sudden or jarring. When something thrums, it has a kind of alive, energetic quality to it, even if the sound itself is quiet or low.