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

the computers hummed

be in a state of great activity

the house was humming with preparations for the dance

smell unpleasant

when the wind drops this stuff really hums

a low, steady continuous sound

the hum of insects

a low hum of conversation

used to express hesitation or dissent

‘Ah, hum, Elsie, isn't it?’

‘Hum. How long did you invite her for?’