Translated as "members-only," signifying content exclusive to the VTuber's paid members. YouTube has a paid membership system for eligible YouTube channels that allows access to certain perks and content unavailable to public viewers; such content is classified as "members-only." This includes members-only messages, emotes, videos, streams, and other content. Commonly shortened as メン限 (mengen). Can also be spelled as memba gentei, menbaa gentei, or menbā gentei.
▸ "Kanata said that she's doing a "menba gentei stream," I believe that means she'll do a members-only stream."