A fork of Rural Dictionary
One who eats all their friend's cereral at his/her friends house and eats all the cereral at at Walmart without waiting to pay for it.
Person 1: Would you like a snack? Cereal Killer: do you have cereal? Person 1: yes... Cereal Killer: (runs away) (Comes back with all the cereral his/her friends have and eats it in under 5 minutes)