“Bakage” (バカゲー) means “stupid game” in Japanese. It’s a classification that’s sometimes confused with “kusoge” (“shit game”) though there are some differences. The main distinction is that a bakage marker isn’t an indication of quality, as some excellent games can be bakage. It’s more of a signifier of strange content. We separate this from the “Wacky / Over the Top” classifier as being the difference between “silly” and “weird/strange”.
There are two major reasons a game can be classified as bakage:
(1) The game concept is extremely bizarre. (See: Choaniki)
(2) The game seems normal at the outset but has lots of strange elements to it. (See: tons of stuff by Data East).
Further reading can be found (in Japanese) at dic.nicovideo.jp/a/バカゲー