How is this example an adjective?

Question

The New Oxford American Dictionary defines one sense of drag to be:

Clothing more conventionally worn by the opposite sex, esp. women's clothes worn by a man: a fashion show, complete with men in drag | [as adj.] a live drag show

Now that second bit saying that it is an adjective raises my eyebrows a bit, because that example doesn't look like an adjective to me. I parse that as

a     live  drag show
det.  adj.  noun compound

And I feel this interpretation is vindicated if we contrast sentences like

The show will be so extravagant.

with

*The show will be so drag.

Here I replaced an adjective (extravagant) describing a "show" (the same noun in the sentence provided by the dictionary) with "drag" and got a sentence that seems to me to be ungrammatical. If "drag" were being used as an adjective in the example sentence then it should be separable from the noun it modifies, and it seems to not be. And this evidence is completely congruent with a noun compound understanding of the phrase.

Now to be a little less naïve, I do definitely see how one could think that drag is an adjective in the sentence. My perspective is quite different from a monolingual English speaker who did not spend a large amount of time in school diagramming sentences. It is a word right before a noun that modifies it, which is basically how adjectives work most the time. And I could definitely see it being a pragmatic choice on the part of the dictionary to cater towards a simpler more approachable understanding. However the issue I see with this is that English allows noun compounding with basically all nouns. And the NOAD does not list every noun this way. So there must be something special about the word it is trying to tell me, but I don't know what it is.

So my questions here are: What's going wrong? Have I misread the dictionary? What is the dictionary trying to tell me.

Answer 1

To me, what the dictionary is telling you is that the word "drag" is most commonly used as an adjective (or as a noun adjunct to use the technical term*).

While "drag" is a noun in its own right, it is most commonly seen as a modifier to other nouns, particularly as "drag act", "drag artist" or "drag show".

The use of "drag" as a noun in its own right is so uncommon in everyday English that most native speakers would be confused if you said something like "this box contains some drag".

*See the comment by user 66974.

Answer 2

In "a live drag show", both "live" and "drag" modify "show", and both are therefore adjectives.
The show in question is a show exhibiting people dressed in drag, or a "drag show". Same as if you were to say "a fashion show" -- a show exhibiting fashions; or "a car show" -- a show exhibiting cars.

Now you could also say, "a live car show", to distinguish this particular "car show" from a video car show. But "car" still modifies "show", and distinguishes it from a "dog show", "a boat show", "an arts & crafts show", etc. Same with "drag".