What does JDM mean/stand for

i always hear JDM, is that just j-spec or some thing?

jdm means its from japan: Japanese Domestic Market.

its usually geared towards higher output at the cost of higher emissions, which is why we dont get it here in america.

japanese domestic market
or
the shit from japan not the cheap generic american shit
hey b16 can i have your motor?

if you have an ungodly amount of money to pay for it.:D

and the ammount is?