hum - definition and synonyms

verb 

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/hʌm/
present tense
I/you/we/theyhum
he/she/ithums
present participlehumming
past tensehummed
past participlehummed
  1. 1
    [intransitive/transitive]

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    to make musical sounds with your lips closed

    If you don’t know the words, just hum the tune.

    1. a.
      [intransitive] to make a low continuous sound

      The fridge hummed in the kitchen.