This may not be what your after but I'll give it a hoof.

(A \ B) is defined as A not B.

I.e. IF A was the set {1,2,3,4,5} and B was the set {2,3,4} then (A \ B) would be {1,5} since neither are in B.

So if we do this with your problem we get...

(Deadstar \ JG) means Deadstar but not JG...

So ((Deadstar \ JG), Football) means...Deadstar likes Football and JG doesn't.