A cool box is an insulated box that keeps food cold. Pack the cool box, a cool box for the picnic.
It keeps cold in rather than making any, so what goes in warm stays warm. Filling the gaps is what makes a cool box work, since air warms far faster than food.
1nouncool boxAn insulated box that keeps food cold.
“The cool box held the milk for two days in the tent.”
cool box is a container.
Also accepted in games: cooler
coolbox comes from cool + box.
Etymology from Wiktionary, CC BY-SA
Practised in Containers & Packaging