If your mother is Jewish then you are Jewish unless you convert to another religion other than Judaism.
Or, If you convert to Judaism (a religion) then you are Jewish as long as you don't subsequently convert to another religion.
If a black or Asian woman converts to Judaism then her children will be considered Jewish even if the children aren't religious, so it's not a race.
A recursive definition uses the word being defined within the definition. The recursion ends at an initial condition, which, in this case, would be Abraham.
So, the other part of the definition is that you are Jewish if you make a convenant directly with God as Abraham did.