Dictionary.com defines ethnocentrism this way:
1. Sociology. the belief in the inherent superiority of one's own ethnic group or culture.
2. a tendency to view alien groups or cultures from the perspective of one's own.
Informally defined, ethnocentricity means being so totally oriented to your own ethnicity and culture that you think that's the only right way to be and all the others are inferior or invalid. Maybe you don't even recognize or acknowledge other ethnicities and cultures or know anything about them. Ethnocentricity can make a person reject anything that's not what he or she was brought up with and taught, whether it's beliefs and values or food and dress. It works against understanding, tolerance, and peaceful coexistence.