Definite volume refers to something which has a consistent, unchanging volume, which in practical terms may mean a static mass and density, or a predetermined shape, either of which will dictate volume. A cube with side length l has a definite volume because it can only be exactly one size.
One cup of raw plantains or one medium sized raw plantain contains: ~180-200 calories, 0.5 g total fat, 47-50 g carbohydrates, 3.5 g dietary fiber, 22 g sugar and 2 g protein. Because of it's high carbohydrate content, you need to monitor your portion, otherwise your blood sugars will spike.
Plantains are a nutritious source of carbohydrates. Plantains are in the same family as bananas. They look similar, but they are starchier and are usually only eaten cooked. Plantains can be used when green, yellow or so ripe that their skins are black.