Baby pushes poop out. If a baby is eating, behaving, and growing fine... But has loose poops that can hit a target 18 inches away, he may be normal, especially if breastfed. Some breastfed babies have loose stools (a bit looser than spaghetti sauce). If he likes to push his poop out, it will squirt out fast enough to hit mom or dad. If he is very gassy, has smelly poop, or is not growing well, a doctor should evaluate.
Poor digestion. The baby large intestine is designed to retreive water from the mix of enzymes & debris left over from digestion. If the baby cannot digest some materials, like milk sugar or lactose, it pulls water thru the system and may be forced thru under pressure. The same pressure that propells a soft stool, will shoot watery poo out the bottom. Your best bet is to confer with the dr about the problem.