Is disinvite slang or sloppy grammar?

"Disinvite" is not slang but rather a formal word that means to revoke an invitation.

However, it's not commonly used in everyday language. People usually use other phrases like:

* "Uninvite" (more informal)

* "Rescind the invitation" (more formal)

* "Withdraw the invitation" (more neutral)

* "Tell them they're not welcome anymore" (very informal)

So, while "disinvite" isn't grammatically incorrect, it can sound a bit awkward or formal in casual conversation.