What does the word obachan mean?

'Oba-chan,' (also could be called 'Oba-san') means aunt in Japanese, this is used when refering to someone else's aunt, or your own aunt in a polite manner. Though this is rather used, because it also mean 'middle aged woman,' and can be taken offensively for that reason.

I noticed several people said it means grandmother. This is incorrect, they got it confused with 'Obaa-chan,' or 'Obaa-san,' which is the formal way to refer to your grandmother or when speaking about someone else's grandmother. It also means 'female senior citizen,' though is not taken offensivley, like 'Oba-chan,' is.

I know a lot about Japanese culture, and am 100% sure this information is accurate, I have several sources if anyone doesn't believe me.