Words used by Japanese people that sound/look like English words, but have different (sometimes completely different) meanings. Eg. kanin-suru (first part sounds like "cunning") refers to cheating on a test, but "cunning" in English refers to a general skill for getting what one wants or for deceiving.
Westerner: In Japan, do you live in a house?
Japanese: No, I live in a *mansion*.
Westerner: Wow! a very big house for rich people???
Japanese: No, *mansion* is a home in a building.
Westerner: Oh! You mean an apartment/flat/condo!
Japanese: Ok, sure. In Japan, people call them *mansions*.
Westerner: Oh, I see - *mansion* is Janglish!