UNKOSHER is a term used to describe food that does not conform to Jewish dietary laws. It is derived from the Hebrew word 'trefa' which means 'FORBIDDEN'. TREF is the four letter crossword solution for UNKOSHER, and it is an acronym for 'Totally FORBIDDEN Religiously Eating Food'. This term is used to describe food that is not allowed to be eaten according to Jewish dietary laws, such as pork, shellfish, and certain types of seafood.