1.
boisterous revelry; noisy partying; rowdy merrymaking
Loud, exuberant celebration or partying, typically involving drinking, singing, and general noise. Often implies excessive or disruptive merriment.
"どんちゃん" is an onomatopoeic expression imitating the sounds of drums and cymbals (太鼓のドンドンと鉦のチャンチャン), suggesting festive noise.
Common patterns
The word has a slightly negative or exasperated tone when used by someone not participating, but a fun, self-deprecating tone when used by the participants themselves.