1. the state or quality of being anfractuous. [ WHY do they do this?!?! ]
LOL! Why indeed. We hates that.
2. a channel, crevice, or passage full of windings and turnings.
Those (1 and 2) definitions would seem to make the word a noun. I checked and both dictionary.com and my beloved Merriam-Webster.com list it as a noun. In your post, you've listed it as an adjective. I would have sworn you copy and pasted this stuff Mxy! Or are you rebelling and calling it an adjective anyway... What would Geoffrey K. Pullum have to say about that?!
2: a winding channel or course ; especially : an intricate path or process (as of the mind)
Merriam-Webster! I was wondering if it could be something intangible, but I needn't look any further than MW, it has all the answers.
I have to think of a sentence. I am determined to use the word as a singular.
bbl