When you prevent a freind from hooking up with a tranny, carrier, or someone too ugly to forgive. Referring to the shock on the dreaded "morning after"
Dude we totallt had to shock block you last night at the club. That girl had an adam's apple and huge palms.
When someone walks in on another person masturbating and said person has seconds (if not less) to cover up.
I was butt naked when my girlfriend walked in on me, but I shock blocked with the blanket, pushed the lube off the nightstand and she didn't even notice!