There are a number of things commonly referred to as a shield:

• A shield is a protective device, meant to intercept attacks. Usually the term refers to a device that is held in the hand.
• In police fiction or police dramas, "shield" is sometimes used as slang for a police badge (i.e., "Give me your shield and your sidearm, you're off the case.").
• A shield (electronics) is a housing, screen, sheath, or cover that substantially reduces the coupling of electric, magnetic, or electromagnetic fields into or out of circuits or transmission lines. See cable modem, coaxial cable
• A shield (heraldry) is the principal portion of a heraldic achievement or coat of arms. Figures and patterns are depicted emblazoned upon the shield in many arrangements.
• A shield (geography / geology) is a large Archaean (Precambrian) rock mass at the centre of a continent, for example the Canadian Shield
• A shield (science fiction) is a fictional device that use energy fields to protect a person or spacecraft.
• A shield (Star Trek) is an energy device used in Star Trek, and other science fiction universes, to protect spacecraft during combat.
• A tunnelling shield is a protective structure used in the excavation of tunnels through soil that is too soft or fluid to remain stable during the time it takes to line the tunnel with a support structure of concrete or steel.
• The Shield is an American police drama television series aired by the FX Network.
• A Human shield is a military term describing the use of civilians to deter an enemy from attacking certain target.
• A heat shield is a protective layer on a spacecraft or ballistic missile that is designed to protect it from high temperatures.
• Radiation shielding protects people or electronics from radioactivity.
• S.H.I.E.L.D. is an international intelligence agency in the Marvel Comics universe headed by a director named Nick Fury. The meaning of the acronym has varied over the years.
• The metro Detroit restaurant Shields serves unique Detroit-style pizza
• The Shielding effect in Chemistry is a reduction in effective nuclear charge on an electron caused by the repulsive forces of other electrons between it and the nucleus, in an atom.