Concrete terms refer to objects or events that are available to the senses. [This is directly opposite to abstract terms, which name things that are not available to the senses.]
Examples of concrete terms include spoon, table, velvet eye patch, nose ring, sinus mask, green, hot, walking.
Examples of abstract terms include love, success, freedom, good, moral, democracy, and any -ism (chauvinism, Communism, feminism, racism, sexism).
I would say that “This burn is almost as bad as racism.”