hum

US /hʌm/
UK /hʌm/
"hum" picture
1.

make a low, steady continuous sound like that of a bee

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The refrigerator started to hum loudly.
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Bees hum as they fly from flower to flower.
:
dronebuzzmurmurthrumvibrate
2.

sing with closed lips, without articulating words

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She likes to hum a tune while she works.
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He was humming softly to himself.
:
croonmurmursing softly
1.

a low, continuous, and indistinct sound

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The constant hum of the air conditioner was annoying.
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I could hear the distant hum of traffic.
:
dronebuzzmurmurthrum