Incretin (417524005) Definition insulinotropic peptides released by the gastrointestinal tract in response to food; stimulates insulin secretion and inhibits glucagon secretion. [from CRISP]
In simple terms, racism is the belief that distinct human races exist and that one race is superior to another. This definition is generally agreed by the Oxford English Dictionary, Merriam-Webster Dictionary (USA) and the Macquarie Dictionary (Australia).
Racism appears to be a word of recent origin, with no citations currently known that would suggest the word was in use prior to the early 20th century. But the fact that the word is fairly new does not prove that the concept of racism did not exist in the distant past.