Aneurysm, miliary: An aneurysm is a localized widening (dilatation) of an artery, vein, or the heart. At the area of an aneurysm, there is typically a bulge and the wall is weakened and may rupture. The word "aneurysm" comes from the Greek "aneurysma" meaning "a widening." A miliary aneurysm is tiny like a millet seed. (Millet is a cereal grass. Its seed is about 2 millimeters in diameter). Miliary aneurysms tend to affect minute arteries in the brain and, in the eye, the retina.