JFTR, McJob doesn't seem to appear in the 11th ed. of M-W Collegiate, but can be found in their unabridged:
a low-paying job that requires little skill and provides little opportunity for advancement

and it doesn't fare much better in AHD4:
Slang A job, usually in the retail or service sector, that is low paying, often temporary, and offers minimal or no benefits or opportunity for promotion.

-joe (McRet.) friday