from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Originating in a place other than where it is found.
- adj. Buried or found in a place remote from the site of formation.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. of rocks, deposits, etc.; found in a place other than where they and their constituents were formed
Ancient Greek ἄλλος (allos, "other") + χθών (khthōn, "earth, ground") (Wiktionary)