"guest discussion" is a correct and usable phrase in written English.
You can use it when referring to a discussion in which the participants are mostly or exclusively guests (i.e. people who are not part of the regular group). For example, "The guest discussion on the new policy went on for over an hour."
The guests' discussion takes place over a set of beer pong cups half-filled with frappuccino, with a giant ball of sugar serving as the beer pong ball.
After listening for almost an hour to his guest's discussion of the difficulties involved in keeping fund prices fresh and fund orders honest, Prof. Marco Avellaneda threw up his hands.
Each class contained a 1-hour lecture followed by a 90-minute guest panel discussion and a networking session with three or four professionals.
Three education classes of mostly prospective teachers provided instruction on issues related to Lesbian- and Gay-identified (LG) youth in schools, including readings, a video, a guest speaker, discussion, and writings.
Univision's "Al Punto" offers a full line-up of political guests, featuring discussions with Carlos M. Gutierrez, former commerce secretary and trade policy adviser for the Romney campaign; Henry G. Cisneros, former secretary of housing and urban development; and Gabriela Domenzain, director of Hispanic press for the Obama campaign.
The I-House hosts an International Coffee Hour every Monday night that class is in session from 6 to 7 pm, hosting both residents and their guests for discussions.
Bill Simmons was talking about A-Rod on his ESPN podcast the other day with Chuck Klosterman or maybe another guest, when the discussion turned to how A-Rod should follow Kobe Bryant's lead and embrace his unpopularity.
Catch a preview of Daft Punk's TRON: Legacy soundtrack, Russell Brand on My Booky Wook 2, Colin Firth steps in as a guest DJ, a discussion of logos gone wrong, 21 DJs list their top 10 albums of 2010, tips on how to exercise in holiday traffic and much more on KCRW's December Top 10.
Place chairs in a circular fashion to equalize guest and promote discussion.
