Oscar Horta has argued that speciesism is wrong by definition. In his view, there can be no more substantive debate about the justification of speciesism than there can be about the legality of murder, for it stems from the definition of "speciesism" that speciesism is unjustified just as it stems from the definition of "murder" that murder is illegal. The present paper is a case against this conception. I distinguish two issues: one is descriptive (Is speciesism wrong by definition?) and the other normative (Should speciesism be wrong by definition?). Relying on philosophers' use of the term, I first answer the descriptive question negatively: speciesism is a purely descriptive concept. Then, based on both its main functions in the philosophical and public debates and an analogy with racism, I answer the normative question negatively: speciesism should remain a purely descriptive concept. If I am correct, then speciesism neither is nor should be wrong by definition.