This chapter is dedicated to Ockham's semantics of real definitions, a topic that has not attracted scholarly attention, but merits comment since it reveals an important point of Ockham's resemblance nominalism that has been little discussed. Indeed, up to now studies of Ockham's concept theory have been limited to his theory of species specialissima concepts, the core of his answer to realism about universals. In this paper, I suggest that Ockham cannot explain why speakers use concepts of higher generality, namely genus concepts, without appealing to a semantics of real definitions that leaves room for the possibility that the same term be defined by several real definitions that are co-extensive but, except in one case, not synonymous with each other.