Help solve a adjective/noun disagreement

[Supersetoy]

Yesterday my friend created his own slang term, "Assatall" meaning "That girl has no assatall". Stupid, I know.

But he defined it as a noun. Half of us thought it was an adjective (claiming that the slang term badonkadonk was a adjective) and therefore assatall being the opposite of badonkadonk - both were therefore adjectives.

I pointed out the sentence, "I have a widescreen". And this is where the confusion comes in. "Widescreen" describes the TV/Monitor/etc. But in that sentence does "widescreen" become a noun? Or does it remain an adjective? Or is this sentence even grammatically correct (my word editor doesn't give me a green squiggly line)? After 2 hours of searching yesterday and today, I still cannot find anything online to prove my friends wrong.