discussion - argument
If you have a discussion with someone, you have a serious conversation with them.
After the lecture there was a lively discussion.
You say that you have a discussion about something or a discussion on something.
We had long discussions about our future plans.
We're having a discussion on nuclear power.
Don't use discussion to refer to a disagreement between people, especially one that results in them shouting angrily at each other. This kind of disagreement is usually called an argument.
We had a terrible argument, and now she won't talk to me.
I said no, and we got into a big argument over it.