autochthonousPronunciation: /ɔːˈtɒkθənəs/Definition of autochthonous adjective (of an inhabitant of a place) indigenous rather than descended from migrants or colonists. Geology (of a deposit or formation) formed in its present position. Often contrasted with allochthonous.autochthonous in other Oxford dictionaries Definition of autochthonous in the US English dictionary