bitter

Something that tastes bitter is unpleasantly strong and harsh on your tongue when you eat or drink it.

When we talk about food, people often use the word "bitter" in a way that's similar to saying it's sour. But while sour things are just sharp and tangy, bitter things are usually more intense and overpowering. For example, if someone says their coffee is too bitter, they probably mean it tastes strong and unpleasantly harsh. On the other hand, some people like the taste of very dark chocolate because it has a deep, rich bitterness to it.