- An electrical disturbance which is generally caused by the frequency of the AC supply, or by one of its harmonics. This may occur, for instance, when the output of a power supply is not properly filtered. In an audio frequency system, hum may manifest itself as a sustained low frequency audible disturbance. In a TV receiver, such a disturbance may result in horizontal hum bars.
- verb (to) fart. Especially popular in Australia, this jocular term probably relates to the surreptitious sound rather than the colloquial meaning of hum as ‘stink’.