Definition of scary card
In French, a "scary card" would not translate to "a scary card". A scary card is a card that over-dynamizes a painting. If a flop is 8-9-T with 2 spades and the turn is a J of spades, the J of spades is a scary card. In other words, on this card, all players will have to be careful because the hand possibilities are enormous.
A scary card can turn a board into an scary board
Let's take a flop as 7-T-J with two spades. Here, the board offers several prints. Let's now imagine a turn that would be a "scary card" and that would transform this dynamic flop into an scary board: an 8 of spades. With the 8 of spades, our opponent could have several combinations of 2 pairs, he could have several straights, he could have one color. A scary card is a card that makes the board scary, i.e. a board on which the possibilities are enormous. On the one hand, when a player bets on an scary board or a scary card, he must be given credit. But on the other hand, scary boards and scary cards are excellent candidates for bluffing. If you bluff a scary card and your opponent has nothing, he will often give you credit and fold.