diffy Adjective; a nickname or word used to describe a very adorable but stubborn boyfriend who knows his amazing girlfriend is right but is always being difficult at realizing this fact. ; > Girlfriend: Hey Baby! Look at this puppy it's so cute can we keep it?! I wanna name it Tyra <3 ; > Boyfriend: No! We are not naming that dog Tyra. The only way that's happening is if that puppy is brown :) ; > Girlfriend: But I want a cute white puppy like this one! * shows pic ; > Boyfriend: no! The brown puppy or nuthin. ; > Girlfriend: ahhh fine you win Diffy. You're such a Diffy. ;