acronym; Granny I'm Not Proud Of. The opposite of milf, the result of believing that 'any hole's a goal'. An rough looking older woman that you ended up having sex with. A GINPO could be what you wake up with, with a hangover when you thought you'd got some MILF the night before whilst wearing beer goggles. Definitely something you would not introduce to your mates.
I got laid last night but I'm not going there again; she was a ginpo.