What is your definition of racism?

Making any unfounded assumption based on race, or treating someone differently solely because of their race. 

It's discrimination against or mistreatment of someone because of their race.  

There is no real definition. People who scream Racism will use their own interpretation of the word, without understanding what Real Racism is.  

People will scream Racism is you are against Mexicans. Mexican is NOT a race. Or the Folks that hate Jews. Judaism is Not a race. Black, White, Yellow, Red. THOSE are races. Nationalities are not. 

Just being white is enough for the liberals.

Racism is the belief that one group of people is better than another.  It could be based on color or ancestral origin. It can be acted on individually (how you treat people) educationally (how and if you represent others in their schooling ) communally (diversity in your neighborhood) and systemically(economics, legal, other systems) 

Racism is a spectrum — you might be overtly burning crosses, covertly  calling voter suppression fairness when in reality it just benefits your party that is the hegemony, subconsciously picking a job candidate that is more a “fit” because they are more like you, or only picking people of color to prove you aren’t racist.  

For many of us the biggest issue is to recognize how racism has benefited us, may affect our behaviors, recognize the need to change, and learn how to move from “not a racist” to being an ally who is an anti-racism advocate.   

It is wise to understand that Godel's Incompleteness Theorems guarantee that in a sufficiently axiomized definition, there will always be unprovable truth (and falsity) claims in the definition's domain.  The work-arounds are at least three:  renormalize by re-axiomizing; frame a second axiomized definition that "explains" the unprovable t/f; accept the first definition as FAPP (for all practical purposes).

So, when dealing with the definition of "racism," first be clear as to the convo's definition of "race"; some possibilities include the biological, which at finer levels shows there is one race--Hom0 sapiens--which itself has ~ 2-6% Neanderthal species genome, and also other inter-species genes e.g. of Denosovians, a species previously found in Tibet and elsewhere, and which helped the evolution of Tibetans' unique O2-gathering ability (up to 7-8% Denosovian genes in Papuan humans have been identified); a yet-unidentified species which lived in Africa, etc.

The more obvious biological distinctions among the human species tend to have developed of environmental factors; e.g. as Asians migrating from a specific sub-race of Africans (with subsequent re-migration of Asians into Africa, which inter-breeding has given East Africans a 25% Eurasian genome).  Conditions in Asian, particularly Chinese, areas, helped select for increased family stability, wider pelvises, larger cranial birth size, etc.  Similar, although not identical, differentiations occurred among the European lineage.

Likewise, another separate group of Africans became the European group or "race;" as both the Asian and European Africans migrated about 60,000 years ago to their respective destinations, each group inter-bred with the Neanderthal and Denosovian species already there, and with a yet-unidentified third human species.

In passing, a recent discovery has identified a Denosovian-Neanderthal individual in the fossil record now named "Denny."

Fast forward to the present illogical and abusive misuse of "race" as a Marxist agit-prop tool.  That psyops shtick continues to attempt to affix a class + race guilt to "whiteness" and "white privilege," as sadly laughable as the "Jews are subhuman descendants of apes and pigs" of recent National Socialism and wrong-path Islamism.  To black-list a whole class/race/ethnic group is despicable, illogical and destructive.

The recent pseudo-sociological constructs argue from the major premise of white oppression, and are very inaccurate.  It is helpful to recognize that the classist charge of so-called "racism" in the U.S. is presently primarily an illogical, infantile leftist dog-whistle mostly tending to help the current erroneous emo-"thinking" which is attempting to justify trashing of productive standards of behavior proven effective the world over, in the name of "social justice," but which actually weakens the United States.

Even a classically popular book such as Sowell's "Black Rednecks and White Liberals" will help clear the current miasma-fracas.  

Considering another race either morally or intellectually inferior.

Making any decision based on race alone (i.e. without considering other factors).

Racism is disrespecting people of a particular group or race due to hate and intolerance which means to be a pathetic human being. 

Any degree of dislike and in any form expressed towards a person influenced by their race.