NOUN (3)

1. the act of shielding from harm;

2. a shield of lead or concrete intended as a barrier to radiation emitted in nuclear decay;

3. shield consisting of an arrangement of metal mesh or plates designed to protect electronic equipment from ambient electromagnetic interference;

The Collaborative International Dictionary of English v.0.48:

Shield \Shield\, v. t. [imp. & p. p. Shielded; p. pr. & vb. n.
   Shielding.] [AS. scidan, scyldan. See Shield, n.]
   1. To cover with, or as with, a shield; to cover from danger;
      to defend; to protect from assault or injury.
      [1913 Webster]

            Shouts of applause ran ringing through the field,
            To see the son the vanquished father shield.
                                                  --Dryden.
      [1913 Webster]

            A woman's shape doth shield thee.     --Shak.
      [1913 Webster]

   2. To ward off; to keep off or out.
      [1913 Webster]

            They brought with them their usual weeds, fit to
            shield the cold to which they had been inured.
                                                  --Spenser.
      [1913 Webster]

   3. To avert, as a misfortune; hence, as a supplicatory
      exclamation, forbid! [Obs.]
      [1913 Webster]

            God shield that it should so befall.  --Chaucer.
      [1913 Webster]

            God shield I should disturb devotion! --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

shielding
    n 1: the act of shielding from harm
    2: a shield of lead or concrete intended as a barrier to
       radiation emitted in nuclear decay
    3: shield consisting of an arrangement of metal mesh or plates
       designed to protect electronic equipment from ambient
       electromagnetic interference

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "shielding":
   blanketing, cloaking, coating, covering, custodial, defending,
   defensive, enveloping, fostering, guardian, guarding, immunizing,
   parental, preventive, prophylactic, protecting, protective,
   safeguarding, screening, self-defensive, self-preservative,
   self-protective, sheathing, sheltering, shrouding, tutelary,
   veiling, vigilant, watchful, wrapping