Is this noun used as an adjective?

Solution 1:

When a noun is used this way it is called an attributive noun or noun adjunct.

One big difference between attributive nouns and adjectives is that while an adjective is predicative, i.e., a big dog is big and is a dog, a points victory is not points, but rather it is a victory when using points as the determining factor.

Solution 2:

As I've mentioned in a comment to another post, it's probably fairer to say that "adjective" ~ "noun" form ends of a spectrum rather than mutually exclusive categories.

However, on balance, reasons for saying that "points" is more "noun like" in this case would include:

• the fact that "points" is marked as plural, whereas e.g. the plural is not possible in "a yellow/*yellows victory"
• the prosodic difference between "a points victory" vs e.g. "a clear victory"
• the ungrammaticality of "*the victory was points" vs the grammaticality of "the victory was clear"
• the ungrammaticality or oddness of "*the score, points victory" vs the grammaticality of "the clear, resounding victory"
• combined with the observation that canonically "adjective-like" words go before canonically "noun-like" words, the observation that "a clear points victory" is grammatical, whereas "*a points clear victory" is not.

None of these obesrvations on its own would be a "smoking gun", but combined, they suggest that "points" is towards the "nouny" end of the spectrum in this case.