1. Shocked at being slapped by someone you would least expect it from. The resulting astonished reaction is usually more intense than the physical pain.
2. The equivalent of being emotionally gagged. Caught completely off guard to the point of not knowing how to respond. Speechless.
"I can't believe I was gaggle slapped! He used to be such a sweet boy... what happened to him?"
"I never expected her to react that way. I felt like dying right then and there. Completely gaggle slapped... now what do I do?"