[uh-lok-thuh n, -thon]
a geological formation not formed in the region where found and moved to its present location by tectonic forces.Compare autochthon(def 3).
Origin of allochthon
First recorded in 1940–45; back formation from allochthonous
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019