What do you call a feature that always has the same value? Is there a standard term for a feature that always has the same value, i.e. that can be discarded without loss of information?

For example I am trying to classify cats vs dogs, and every example in my training set has has_two_eyes=true.

I am thinking something like "useless," "redundant," "constant," or "degenerate," but I don't know what the standard terminology is here.
I think there are a few terms, but the one I have seen most often is "Zero Variance Predictor" or "Zero Variance Feature"