Literally, the term translates to “no words.” However, the modern meaning is far more potent. It doesn't just mean you are silent; it means the situation is so bafflingly foolish or illogical that it doesn't deserve a verbal response. You have been rendered speechless by absurdity.
无语 is a cornerstone of modern Chinese internet and youth culture. While its characters are ancient, its current usage as a standalone expression of exasperation exploded with the rise of social media. In Western culture, someone might say “I'm speechless” to convey positive awe (e.g., at a beautiful view) or negative shock. 无语 is almost exclusively used for the latter, and specifically for situations involving foolishness or frustration rather than tragedy or fear. The closest English equivalents aren't single words but cultural expressions:
Using 无语 is a quick, non-confrontational way to signal strong disapproval or disbelief. It says, “What you just did or said is so beyond reason that I'm not even going to waste my breath arguing.” It is a powerful social tool for judging a situation as hopeless or ridiculous without starting a direct fight.
无语 is highly informal and extremely common in everyday communication, especially among younger people.