Definition of "unpierced"

There was not one of these left standing unpierced by bullets.

1885, Ulysses S. Grant, Personal Memoirs of U. S. Grant, Complete‎

When he was rushed back to the hospital two weeks ago the Sun-Times referred to the unpierced "veil of secrecy" that has surrounded him since his stroke in March.

2006 June 23, Michael Miner, “There Oughta Be a Law; Small Victories”, in Chicago Reader‎