888888888 is a term used on Nico Nico Douga to mean applause or to clap.
In Japanese the number 8 is pronounced as "hachi", which sounds close to "pachi" (パチ), which means "to applaud or clap".
Eroipu (エロイプ) is a portmanteau of the words "eroi" and "Skype" and means dirty talk on Skype. Also, it can be described with so many things; such as animals, certain foods and clouds in the sky. Gasshou (合唱) means "chorus" in Japanese, and is used on Nico Nico Douga primarily to denote fan-made choruses of covers ranging from 4 to 300 utaite.
These are not organized by the utaite themselves; however, the video makers almost always credit each included utaite. gdgd (グダグダ, gudaguda) is a term that means "lazy" or "sloppy", etc.
In a namahousou, unnamed users are anonymous, and have to change their settings to be viewable as an individual user to the host and other users.
2525 cafe is a Nico Nico Douga cafe located in the Nico Nico Douga studio building headquarters in the heart of Harajuku district, Tokyo.
It is usually used at the end of a video to congratulate the user for a good job on the video. Hiwai (ひｙ/卑猥)means doing something (talk, acting of, etc.) sexual.