Whites/Blacks who make dating Blacks/Whites into a fetish activity. That is, they're consumed by the mythology behind a person's race (ie virility of Black men, the Black penis, Blacks as more primitive and closer to the mythical Jungle, etc.) than the person him/herself. Many are attracted to such relationships because they perceive them as transgressive and are turned on by that.
Not all Black-White relationships are based on Jungle Fever. However, one may be able to identify relationships that are based on Jungle Fever by analyzing the couple's dating history. For instance, if a White person who lives in an area with few Blacks has only dated Blacks, then it's likely that that person has Jungle Fever.
Generally considered a derogatory term that hints at past colonial relationships between Blacks and Whites, where White colonizers enter, with fascination, the African Jungle in order to learn from and conquer it.
Watch out for that White girl Angela cause she has major jungle fever. She can't keep her eyes off tha brothers, probably because her daddy won't let her date a brother.