It seems that historical definitions of the word "racism" use it to mean something similar to "racial prejudice" and "racial discrimination", without any reference to which race has power or doesn't have power. Whereas there seems to be a growing movement in some sectors to define racism as always being about a race with more power or privilege oppressing a race with less power or privilege in a given society. For example, here was a recent article I read: http://everydayfeminism.com/2013/08/racist-against-white-people/
So, is there any general usage guidance we can give for the word "racism"? Should it now only be used to mean racial oppression of the powerful on the less powerful even though most dictionaries haven't caught up with that sense yet? Or should it only be used in the older sense that most dictionaries list for it? Should it be avoided because of this controversy? Should any user be careful to define his exact meaning if he uses it?