Hidden, covered, censored, blocked
Hidden
hidden
hide
covert, hidden, unseen
covert unseen hidden masked disguised
gunman, assassin, sniper,
sheltered, private, concealed, hidden, unfrequented, sequestered
If you mean letters, it's hidden.
Another word for conceal is to hide, disguise and hold back.
Another word would be drenched, coated or smothered.
hidden, invisible, unseen
help sir