A grating; a grid of wire or a sheet of material with a pattern of holes or slots, usually used to protect something while allowing the passage of air and liquids. Typical uses: to allow air through a fan while preventing fingers or objects from passing; to allow people to talk to somebody, while preventing attack.
User Defined Definitions
"grating that admits cooling air to car's radiator"
"a framework of metal bars used as a partition or a grate"