The act of expending great energy on hating one's self. Its roots are usually found in childhood due to an invalidating environment such as seen in child abuse, or with parents who are addicts, or alcoholics, or in families where mental illnesses may be present. Self-esteem suffers in children subjected to abuse, or emotional abandonment, by the parents.
Some children that are victims do not grow up hating themselves; the difference is that they have a good support system, and some wise adult lets them know that none of it is their fault. Children tend to blame themselves, and unless someone they trust helps them to see it isn't their fault (whatever the family's situation is) they grow into adulthood with poor self-esteem, and guilt, and feeling like the world would be a better place if only they weren't in it.
Self hatred may be evident in many ways in the adult. There may be suicide ideation, and attemps of suicide, self injury, drug use, or alcoholism, reckless behavior, and extreme risktaking. (extreme sports, unprotected sex for example)