When a group of friends sit around a computer and share youtube videos that they have found in the recent weeks, and take turns sharing said videos.

In a Youtube Session, there is an unspoken rule about taking turns, usually in a round robin style, but is often broken when someone exclaims that everyone "has to see" the video they have in mind.

An abbreviation of "Youtube Session" would be "Youtube Sess", with "Sess" pronounced as "Sesh".
"Charlie, great Youtube Session the other night. I didn't know about Wombo Combo until Heather showed me."

"Oh, my, god. You NEED TO SEE THIS VIDEO, TIME FOR A YOUTUBE SESSION"
by Kangaroo captain December 11, 2009
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