trailer cereal Share definition Flag Cereal that comes in giant bags resembling dog food or cat litter bags. Always an off-brand and very cheap. Bubba eats his trailer cereal out of the bathtub because he doesn't have any bowls. trailer cereal by PerCoceT January 20, 2005 0 0 Get merch Get the trailer cereal mug. Buy Now — $32.95 See more merch