Grunge

[bartholomew]

We grunged away in the bedroom.

Could you explain what they did?

[jenstar]

They put on some Nirvana records and jumped up and down, playing air guitar?

[IndieSinger]

The OED doesn't list the verb to grunge away but, as well as giving the definition of grunge music ("A style of rock music characterized by a raucous, often discordant guitar sound, lazy vocal delivery, and downbeat, freq. nihilistic lyrics, and (in later use) influenced by heavy metal and punk rock.") it also lists another meaning: "A general term of disparagement for someone or something that is repugnant or odious, unpleasant, or dull; also, dirt, grime." It also says this is chiefly American slang - is your source American? The verb form could be related to this second definition of the noun grunge.

[tartanwiz]

They shook their heads up and down while listening to inane buzzing sounds.