A person of nationality of the country of Mexico.
Contrary to popular misconception, "Mexican" is not a racial or ethnic group. Though the majority of Mexicans are Amerindians (pure-bloods and mixed-bloods "mestizos"), there are a substantial number of non-Indian Mexicans, such as the Spanish whites that are effectively the ruling class of the country, blacks, Jews, Arabs (Salma Hayek, telecom magnate Carlos Slim), etc.
A "Mexican-American" is a Mexican national in the U.S. Though the U.S. born children of Mexican immigrants usually claim to be "Mexican," this makes no more sense than U.S. born children of Canadian immigrants claiming to be Canadian.
Idiot: Uhm, Vicente Fox ain't brown; how's he former president of Mexico?