noun

• Anything that protects or defends; defense; shelter; protection.
  "Fear not, Abram: I am thy shield, and thy exceeding great reward."
• Anything that protects or defends; defense; shelter; protection.
• Anything that protects or defends; defense; shelter; protection.
  "The earth was excavated from the sunken cylinder; the shield was inserted into it, and the tunnelling began, the target being Wapping, on the opposite bank. The shield was an iron honeycomb containing thirty-six cells within which men dug the wall of mud before them."
• Anything that protects or defends; defense; shelter; protection.
  "Kinetic barriers, colloquially called "shields", provide protection against most mass accelerator weapons. Whether on a starship or a soldier's suit of armor, the basic principle remains the same. Kinetic barriers are repulsive mass effect fields projected from tiny emitters. These shields safely deflect small objects traveling at rapid velocities. This affords protection from bullets and other dangerous projectiles, but still allows the user to sit down without knocking away their chair."

verb

• (ambitransitive) To protect, to defend.
  "Sunscreen shields against the harmful effects of solar rays."
• (UK, intransitive) To shelter; to protect oneself.
  "The government has updated its guidance for people who are shielding taking into account that COVID-19 disease levels have decreased over the last few weeks."
• (electricity) To protect from the influence of.