While the term ‘ethnic group’ (EG) is often used in social studies, its definition differs among researchers. However, little is known about ordinary people’s subjective understanding of this term. We examined this issue in a study on 273 American, British, Mexican and Polish students using open-ended questions. Results indicate cultural differences in patterns of ‘ethnic group’ definitions. U.S. participants predominantly connected EG to race; British participants, to race and culture. Common culture and traditions were dominant in Mexico, while race was much less popular. Poles defined EG mostly as nation, common culture and history, sharing the same land, religion, and language. For the US or UK, ethnic group was more a subgroup within a nation, while in Poland - they represented the same level of categorization. However, other definitions appeared, e.g., people having similar hobbies or living in the same city. Some participants identified EG only with minorities and people different than themselves, which led to denying having any ethnicity at all. Implications for using the term ‘ethnic group’ in social and cross-cultural studies are discussed.