A fight over something so ridiculously stupid that it might as well be a fight between two old women whacking each other with their purses. Granny fights are not gender specific, and most often tend to happen between teenage heterosexual couples, or more often adult gay men. The term, however, is universal.
Robert and his boyfriend had a granny fight over Robert leaving the seat up.
Matt and Meg had a granny fight about Meg stealing all the covers.
Brian and Allen had a granny fight over which game console is better.
A fight between two elderly women. Usually over small and stupid stuff.
I saw a granny fight in the theater.