sour

The green grapes were so sour that they made my eyes water.

(Chinese) 这些绿葡萄太酸了，酸得我直流眼泪。

Smell the milk before drinking it to make sure it hasn't gone sour.

(Chinese) 喝牛奶前闻一闻，确保它没有变酸。

The waiter had a sour expression on his face and gave us terrible service.

(Chinese) 服务员沉着脸，给我们的服务非常糟糕。

He became sour and bitter after losing his business in the financial crisis.

(Chinese) 在金融危机中失去生意后，他变得郁郁寡欢、愤世嫉俗。