Ridiculous glasses with metal frames worn by serial killers in the 70s and 80s, hipsters in the 2010s, and girls with a superfluous E a n their first name.
A human being, usually an adult white male in his late twenties, who has killed four or more individuals in seperate incidents with a cooling off period in between.
Serial Killers come in several types. There are Hedonistic serial killers, who enjoy causing pain and suffering.
Visionary killers are often psychotic, and beleive they are acting on orders from a higher entity.
If left unchecked, a serial killer may degenerate into a spree killer or mass-murderer, which are entierly different things.