This definition, I believe, is fair and consistent with common parlance. In everyday language, racism has never been dependent on which racial group is predominant in a society’s higher positions, nor should it be.
There are those who would like to revamp the word so that only white people can be guilty of racism, using the so-called “prejudice plus power” argument. This not only unfairly places the shame for racism exclusively on whites, but also emboldens those with ill will against white people to profess and promote racism against them.