"Racism is prejudice plus power."
"Anyone of any race can have/exhibit racial prejudice, but in North America, white people have the institutional power, therefore racism is a systematized discrimination or antagonism directed against people of color based on the belief that whiteness is superior. It is insidious, systemic, devastating, and integral to understanding both the history of the United States and the everyday experiences of those of us living in this country.
"Note: A common, incorrect definition of racism is the colloquial definition: 'racism is prejudice against someone based on their skin color or ethnicity and can be committed by anyone.' This is not an accurate definition nor the one used in most anti-racist circles. It highlights individuals' thinking and actions but ignores embedded institutional and cultural systems.
"Non-white folks can be agents of racism as well (particularly when acting as representatives of white-dominated systems, such as higher education) by perpetuating the notion of white superiority and using it to discriminate against other people of color. For example, a black manager at a company may insist that a black employee's natural hair looks 'unprofessional,' or an Asian professor may knock points off the presentation grade of a Latinx student who speaks with an accent."
(Borrowed from Simmons University Anti-Oppression LibGuide)
Another definition, from Ibram X. Kendi, the founding director of the Antiracist Research and Policy Center at American University, is that racism is "a powerful collection of racist policies that lead to racial inequity and are substantiated by racist ideas," and that a racist is "one who is supporting a racist policy through their actions or inaction or expressing a racist idea." These definitions stress the importance of policies in upholding racism and that each of us can choose from moment to moment whether to act in ways that are racist or anti-racist.