The growing interest in Content and Language Integrated Learning (CLIL) has resulted in enthusiasm in and active pursuit of improved methods of foreign/second-language (L2) teaching in Europe. However, the definition and scope of the term CLIL both internally, as used by CLIL advocates in Europe, and externally, as compared with immersion education in and outside Europe, indicate that the core characteristics of CLIL are understood in different ways with respect to: the balance between language and content instruction, the nature of the target languages involved, instructional goals, defining characteristics of student participants, and pedagogical approaches to integrating language and content instruction. We argue further that attempts to define CLIL by distinguishing it from immersion approaches to L2 education are often misguided. The aim of this article is to examine these ambiguities and to call for clarification of the definition of CLIL. Clarification is critical if CLIL is to evolve and improve systematically and if CLIL educators are to benefit from the experiences and knowledge acquired in other educational settings.