Describing an organism that is native to the place in which it is found. Compareallochthonous.
Geology and Earth Sciences
Indigenous; applied to a material (e.g. dripstone, coal) that was formed in its present position. No significant transport has been involved. Compareallochthonous.
Geography
Referring to features and processes occurring within, rather than outside, an environment. An autochthonous rock has been formed in situ; coal is an example.