The term 'UNCLEAN FOOD, BY JEWISH LAW' can be summarized as food that is not considered kosher according to Jewish dietary laws. TREF is a Hebrew word meaning 'FORBIDDEN' and is used to describe food that is not kosher. This includes any food that is not slaughtered or prepared in accordance with Jewish law, such as pork, shellfish, and certain types of seafood. Additionally, any food that has been mixed with dairy products is also considered TREF.