[wao]

Originally Posted by Level E

foo-san is a name you'll probably see a lot. When a douga is removed, the admins upload a douga in its place explaining the reason for removal. These douga are typically have foo-san (a staff member) playing a recorder flute in the background.

Spoiler for Well, if it's not needed...:

I don't guess it's used nowadays since it's been some time since they changed the "this video has been removed" video, but for a while 鬱です (Utsu desu - "It is depressing"?) would be a common slang referring to deleted videos (or something along those lines).

Then there's that 何故殺した (Naze koroshita - "Why did you kill it") → 何故殺たし (Naze korotashi - a somewhat odd sounding misspell) →何故(insert past form of verb that is misspelled) thing, and I never investigated where it comes from except for hearing something vague about Evangelion. So now if something has been deleted you might see 何　故　消　た　し...

Oh, and the quintessential ゆとり (yutori), which refers to ゆとり教育 (yutori kyoiku - "breathing space" education). You can google it up; they basically reduced the content taught in classes so that every kid would understand what they needed properly, and increased more extra-curricular classes. Apparently this actually started since the 70s, but some places say that the first major change came in the 80s and they started introducing five-day school weeks in 1992.
The public is generally rather suspicious and disapproving of yutori kyoiku, apparently, and on niconico douga "yutori" is used as an euphemism for "stupid brat" (I think). AFAIK it's usually meant to insult you as being young enough for that education and having suffered from it.

An alternative if you want to flame youngsters is 平成生まれ (heisei umare - born in the Heisei era, starting from 1989) but I don't see it that often on the videos I watch.

Oh, and there's also 工作 (manipulating) which in a niconico context tends to refer to ランキング工作 (manipulating the video rankings). By default the rankings will show that day's most "favourited" videos in descending order, and sometimes a group of diehard fans/people with no time will get together and purposely add it in their list for one day, remove it before the next day and then add it in again so it keeps staying in the rankings list, even though it may not actually be such an interesting video. For this reason I always look at the "playback" list because it's much more accurate for seeing what people are really interested in.

Maybe this should go to the otaku lingo discussion thread or the Niconico Douga thread in General Chat. I wouldn't mind helping people understand if there are any strange slang words/puns (that is, if I understand them myself... -_-) I could totally go on about the Fuchagi series of cat videos, but that's definitely not otaku lingo.