What is Scare Card in Poker?

A scare card is a community card that is perceived to have made a strong hand for an opponent and generally scares other players in the hand, thus forcing them to play passively and check their hand instead of bet.

For example, if you hold JJ and the flop comes A-5-9, the ace is a scare card as your opponents will have a lot of Ax hands in their preflop ranges.