To emphasize something really good or bad, depending on how it is used in a sentence. Can have several meanings and can be used as a verb or a synonym.
That dude's shirt is not da business!
My husband gave me da business last night for coming home too late.
I love her hair. It is da business!
A trip to a grocery store, convenience store, or gas station for the sole purpose of buying an excessive amount of junk food and sugary drinks, usually with friends. A chud run often happens late at night and ends with everyone involved hating themselves afterwards.