無茶苦茶 is the expression which is stronger version of another word, 無茶. 無茶 means “nonsense”, “ignorant”, or “extremely / beyond limits” and is thought to have originated from an old Buddhist word ムサ. This ムサ has become 無茶 to make pronunciation easier, and the 苦茶 is added to make the sound roll off the tongue more and add emphasis to the meaning. As for why this word uses these kanji, 無茶苦茶 is what’s know as 当て字, e.g. these characters are used only for their sounds, not their meanings.
無茶苦茶 can be used in many ways. As a な-adjective, it can be used to describe things that are a complete mess. For example, we can use it to describe something that is actually messy, like in the sentence “あなたの部屋は無茶苦茶ですね！” or “Your room is messy and dirty.” And we can also use it to describe feelings or mental states. For example, the sentence “彼女に振られて、僕はもう無茶苦茶だ” or “I was dumped by my girlfriend, so I am so devastated” describes someone whose mind if in a state of confusion and feeling ‘all over the place.’
無茶苦茶 can also be used as a noun. In this case, we often translate it as “nonsense”. If we say “そんな無茶苦茶を言わないでください”, that means “Please don’t such nonsense things.”
無茶苦茶 can even be used as an adverb, in a way that means “extremely”. 無茶苦茶大きい for example means “extremely big.”
Since the basic meaning of 無茶苦茶 is “mess”, it ususally has a negative connotation associated wtih it. So be careful in how you use it in a sentence or expression!
After the typhoon, the town was a mess.
He is such a mess. He gets angry quickly and doesn’t keep his promises.