Number of Scenes:
Scenes with this tag involve the victim having their mouth (and or nose) covered with something to prevent them from making noise.
Usually you will see cloth or tape being used here, but some comic writers get creative. It's quite common to see this tag paired with 'bondage'.
It's rare to have a scene with the 'gagged' tag, but no 'bondage' tag.
Finding a scene with a bound AND gagged damsel is difficult. They call it "giving her the full treatment" when such a scene is found.