月末: the end of the month

(idiomatic) can't be undone, can't be saved, unable to recover

Alternative form of 取り返しがつかない

(informal, video games) to lag

Inner Mongolia (an autonomous region of China)

Outer Mongolia

Obsolete spelling of シカゴ (Shikago, “Chicago (a city in Illinois, United States)”)

the Paleogene period

(offensive, Internet slang) Alternative form of 子供部屋おじさん

(offensive, Internet slang) a man whose age is greater than about thirty or forty who lives in one's child room and with one's parent(s).