here is a picture of the fruit, whole...

A citrus tree infected w/greening? Does the fruit smell orange-y, lemony or grapefruit-y? If leaves are asymmetrically mottled yellow & green, that is 1 sign - the shape of that fruit may be another...

Sour orange?

The Tradition has nailed it (I think) :)
After searching for images of "Sour Orange Trees" I think it is a perfect match. I would have liked Lime, or something else, but it says the fruit can be used as you would use a lemon... Thanks for your input.

I do not agree that sour orange can be used - it is bitter, bitter, bitter. My neighbor has a huge tree and I tried to use the fruit - omg, it was horrible!

J marinates meat in sour orange! Adds a nice mild orange flavor to meat, especially pork! Try it!...........:)