I've been using Femap and Nastran for decades, but don't remember this on the spot. It's likely to be moment per radian, because it is a direct "Nastran" entry, rather than being just a Femap model building activity (such as rotating some geometry, which uses degrees). But wouldn't the easiest way to answer a question like this be to build a simple test model? If someone asked this of us as a support question, that's what we would do if we weren't 100% sure. Or look at the docs (Quick Reference Guide), which will have the answer for the element type you've chosen.