Nah, it's a question I like to ask people, not dictionaries/encyclopedias. 
- Edit 1
- Edit 1Before modification by (beat.) at 19/06/2010 03:33:45 PM
Conceptions of race, as well as specific ways of grouping races, vary by culture and over time, effectively functioning as folk taxonomies.
Because of that.
But I guess your answer is "salient visual traits such as skin color, cranial or facial features and hair texture"?