It’s a hood:

This is my second attempt at Maggie Righetti’s three needle bind off and seam process. It worked really well the first time, and gave such a lovely neat seam that it was quite distressing how hard it was to seam the last little bit of the join that had to be done with a needle where the decreases were.

When I was done I was at first pleased, but also a bit puzzled as to why the rows looked so wide apart at the seam. As I lay in bed trying to sleep last night I realised that the rows were so far apart because I cast off on what would have been a right side row. While waiting for an hour or so at the doctors today I ripped out the bind off and the previous row and then bound off again. I am much happier with this version.

The last bit of the seam (which was sewn over the increases) seems to look better binding off a row earlier too, but is still not ideal. I am not sure if I fully understand short rows, but if my understanding is correct then I probably would have been better off using short rows rather than decreases and then seaming the whole hood with the three needle bind off. But it is done now and I am not undoing it again; however, I will know next time I make a hood in this style.