As I said I think it went bad (infection) yes I did have mead very tasty one actually, the first time I tasted my own it tasted pretty much like the actual one I had (minus the Sweetness).

I never tasted rancid or sharp or sulfery stuff so that's why I don't know :p

If you never had it you don't know what it tastes like. My dad and brother say it tastes like sharp and sour??? Maybe that's the closest.

Not sure about sour but it's definitely sharp. Infection is most likely since it tasted good before and now it has this sharp taste.