When I use the word "meeting" it always means a situation where exchanges are happening in real time. In asynchronous forums you can put out a comment and check back later to see if someone has responded. This is NOT a meeting by my definition. There has to be dialogue in a real-time, back-and-forth flow. If it is a chat that is happening while being interrupted by another chat or other activity that is NOT a meeting either. I want a natural, rapid exchange of ideas. A robust dialogue where your primary attention is continuously on that dialogue.
Just so you don't get an unpleasant surprise later—If I require a meeting and you do not follow the definitions below, I will consider that academic dishonesty and, if I learn of it, there will be penalties involved.
Group members are physically present.
Group members are communicating through Skype or conferencing software / Web sites that allows all members to see all members faces.
Groups members are communicating through chats or conference calls of one sort or another. If it is a two member group I can visualize ways that rapid texting would also work and, of course, phone calls work in that situation, too.