To Get a phrase with such outsized relevance in vehicle culture, "JDM" is definitely an acronym for a fairly uninteresting phrase: Japanese Domestic Marketplace. It refers to merchandise built and meant for sale and use within Japan (i.e., not for export). This features anything from autos such as the Autozam https://elevemotors.com/product/jdm-toyota-aristo-2jzgte-2jz-twin-turbo-engine-sale/