You are being "boring"

One day, I was with my friends, and one friend was teasing me. I looked at him, and I said:

- Boring!

My friends looked at me without understanding why I said boring. Then, one friend asked:

- Boring?

I replied: 

- Yes!

Then, they explained to me that boring is something that makes you fall asleep, and annoying is someone or something that makes you irritated. Of course, after that, they were teasing me, and every time they wanted to say annoying they said boring and vice versa.

I made this mistake because boring means "chato" in Portuguese, and this word means annoying and boring. You can say that someone is "chato" when the person is annoying/teasing you, or you can say that something is "chato" when the thing makes you fall asleep.