Spooking is a casino term most often used in a game of blackjack. It refers to a person standing behind the dealer who is trying to peek at the hole card so that they can convey that information to another person or player at the table they are in cahoots with.
There are several different methods of spooking, such as first-basing, front-loading, and hole carding, all of which are performed in a slightly different way but with the same intent.
It goes without saying that an activity like this is illegal. Any person or a group of people caught doing that will be escorted out of a casino and get banned. In addition, players might even face criminal charges, depending on the method of cheating they used or how much money they have won by cheating.