Definition of milk box in US English:

milk box

noun

  • 1A container in which milk is heated in the cheese-making process (rare).

  • 2A box in which milk can be stored to be kept cool.

  • 3A box, (now) especially one on the outside of a house, to which milk and other such items can be delivered.

Origin

Mid 19th century; earliest use found in Scientific American.