A Chinese expression of alarm and anguish. Despite dialectic differences in China, it seemed to be used universally in Eastern and Central China. One of the most commonly heard phrases in Chinese, it can be used to denote anger as well.

Depending on the severity of the incidence, you can drag out the yo part longer. For example:

Aiyooooooooooooo! - Something really really bad just happened

Aiyo! - Not so bad, but it still sucks

It can be loosely translated into English as "Oh no" or "Uh oh", however, it can also mean "Oh shit" or worse. It seems to be a phonetic expression, because in words the characters mean nothing. Perhaps this expression descended from word of mouth instead of writing.

Variation: Ayaah! Drag out the last part accordingly. It has the same meaning. Thanks sensei!