1a broad piece of metal or another suitable material, held by straps or a handle attached on one side, used as a protection against blows or missiles. a sporting trophy shaped like a shield, consisting of an engraved metal plate mounted on a piece of wood: team captain Ben Hall collected the winners' shield a US police officer’s badge. Heraldry a stylized representation of a shield used for displaying a coat of arms. 2a person or thing providing protection:a coating of grease provides a shield against abrasive dirt a protective plate or screen on machinery or equipment: a face shield is sometimes an integral part of a safety helmet a device or material that prevents or reduces the emission of light or other radiation: water is a relatively good shield against cosmic rays a hard flat or convex part of an animal, especially a shell: the horseshoe crab’s armour forms a huge domed shield
3 Geology a large rigid area of the earth’s crust, typically of Precambrian rock, which has been unaffected by later orogenic episodes, e.g. the Canadian Shield.
protect from a danger, risk, or unpleasant experience:he pulled the cap lower to shield his eyes from the glare these people have been completely shielded from economic forces prevent from being seen:the rocks she sat behind shielded her from the lodge enclose or screen (a piece of machinery) to protect the user: cylindrical ducts shield the propellers prevent or reduce the escape of sound, light, or other radiation from (something):uranium shutters shield the cobalt radioactive source