People use the insult "That language doesn't have any grammar". This is completely absurd of course. Grammar is the set of rules which the speakers of the language follow when they speak.

When you say that a language has no grammar, it would be impossible to make a mistake when speaking it. If a language has rules, it has grammar. And since every single known human language distinguishes at least nouns and verbs, every single language has grammar.

In other words, myth busted.