Morgan. In my opinion I would dump it. Once wine is opened it oxidizes and starts to deteriorate. If it had been recorked almost immediately you could have even drank this the next day with just a little deterioration and if you had refrigerated it you could have used it for cooking within a few days. It really wouldn't be fit to drink and therefore it isn't fit to cook with either.

Ann.

I wouldn't dump it....it will for sure be more sour....but makes a great marinade.
Also, the less "head room" in a bottle the better it keeps. So if you have a 1/3 of a bottle left, it will keep better if you pour it into something smaller.
Linda C

I would taste it and if you like it drink it. In the old days wine was not refrigerated after opening.

If it was corked it will be fine. I make wine & very often have some left in the bottle. Most often I will put the cork in & put it in the fridge, but alot of times it sits out & it stays fine.