Is cannibal a word?

Yes, the word 'cannibal' is a word; a noun, a word for someone who *eats* other people, a word for a person.

Typically, eating people is a custom and not as a regular diet. Ritual cannibalism among isolated tribes in the islands of Southeast Asia has been identified as a major source of a virulent brain disease.
Some psychotic conditions can include both serial homicides and cannibalism of victims.