discussion-n; 2 Senses

Sense Number 1: a verbal presentation, analysis, critique

Commentary: DISCUSSION[+activity][+communication][+verbal][+presentation][+critique][+spoken/+written]
NOTE: generally implies a single speaker/writer presenting information

Her discussion of concurrent programming in chapter four is excellent.
The professor's discussion of string theory was inaccessible to most of the audience.
Pete used slides to accompany his discussion of the archeological site in Mexico.
Mary was asked to be on a panel discussion about the World Wide Web. (More of a formal presentation, than a conversation, even though several speakers are involved)

WordNet 3.0 Sense Numbers: 1

Sense Number 2: a directed conversation about a topic

Commentary: DISCUSSION[+activity][+communication][+verbal][+conversation][+directed]
NOTE: implies more than one participant, a conversation about a designated topic

They had a serious discussion last night about their son's drinking problem.
There have been no further discussions about the dog park at town hall meetings.
We had a lively discussion about politics at lunch today.
The specific content of the bill is now under discussion in the Senate. (back-and-forth)
These are topics for future discussion at our next meeting.

WordNet 3.0 Sense Numbers: 2