Diminishing marginal utility implies that as a person consumes more and more of a good or service, the additional satisfaction or utility that the person derives from each additional unit of the good or service decreases. In other words, the more you consume of something, the less additional satisfaction or pleasure you will receive from each additional unit. This is because the more you have of something, the less valuable each additional unit becomes to you. Therefore, the marginal utility of each additional unit consumed decreases as consumption increases.