Not particularly obscure (it’s in AHD), but a new word for me (and Firefox’s spell-checker): adscititious, “not inherent or essential; derivative.” Use it in a sentence? Why, yes, we can:
Despite my meager funds, I started bicycling each Saturday morning to the estate auctions I saw advertised in the paper, where I would take note of wonderful objects to covet, things that might answer my need to be an owner. However, the few crumpled dollars I had stuffed in my jeans kept my attention tied to the boxes of bric-a-brac and potpourri and nearflung gewgaws, which were always assigned to the very end of the auction, when the high-end collectors had already roped their prizes to the roof of the station wagon and driven off. I thrilled to crates of chilly hardware—coffee tins of rusty nails and mismatched bolts and buts, odd attachments, gimcrack, rickrack, and adscititious crap—because at least then my dollar or two would bring me something hefty, clumped, and durable, in good quantity, penny per pound. Sometimes my fifty-cent bid would be enough to claim it all, and I’d sweat to get it home by bike, understanding at last what I really meant by “adscititious crap.”
—William Davies King, Collections of Nothing, pp. 31-32