from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Served with the natural juices or gravy: roast beef au jus.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. prepared or served with the jus from roasted meat
- n. the jus itself, when something is served au jus
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. served in its natural juices or gravy
French : au, with the + jus, juice.(American Heritage® Dictionary of the English Language, Fourth Edition)
French au jus (with the juice) (Wiktionary)
From the adjective, through misinterpretation of it as a noun. (Wiktionary)