1. [n]  the act of shielding from harm
2. [n]  a shield of lead or concrete intended as a barrier to radiation emitted in nuclear decay
3. [n]  shield consisting of an arrangement of metal mesh or plates designed to protect electronic equipment from ambient electromagnetic interference
4. [adj]  actively protective; "provided covering fire for the platoon that was moving up"

SHIELDING is a 9 letter word that starts with S.