A standard unit of size (volume) or mass equal to a Morris Oxford motor car.
Normally used to express incredulity at the comic size of an object or feature.
Dude 1: Jesus - look at the size of that guys head....
Dude 2: it's massive - it's a planetoid of a head ... Etc.
Dude 1: it must be at least 0.8 of a Morris....
Dude 2: Way! Maybe even a full Morris - The Morris!
Dude 1: No Way - a full Morris can bend light it's so massive!!!!