Something no one understands the actual meaning of anymore. People, of all races, tend to cry racist anytime any sensitive issue involving race is mentioned nowadays.
Racism is the act of discriminating against a person or group of peoples based solely on their perceived racial identities, such as "The restaurant had a sign that clearly read 'No Mexicans'"
It is NOT when someone says "hey, that only happened because you're white/black/mexican/whatever".