The word is either non-gradable or non-scalar. I've been hunting around for a linguistic term that's a plain word, not a negative, but can't find one by searching for "gradable" and "scalar".

The difference between these two isn't entirely clear to me. A gradable property is one that something can have to a greater or a lesser extent. A scalar property designates a distinctive point on some scale. Most adjectives are both. Hm.