Definition of flashed
What is meant by "flashed" is a card that would have been flashed. This can happen for a variety of reasons. A flashed card or cards are cards that should have remained hidden but, for one reason or another, were revealed to one or more players at the table. For example, let's say there are 4 players involved in a hand at flop. One player makes a bet, one player calls and one player decides to fold. Falling down, he throws his cards into the discard pile (the muck) and a card is accidentally flashed, i.e. it is face up, visible to one or more players.
What do you do when a card is flashed?
Here, when one or more cards are flashed, the dealer intervenes and makes sure that all players still in the hand can see the card that was flashed so as not to give an unfair advantage to any player. This card will be left face up on the table for all to see. When a player throws his cards in the muck in this way and one of his cards is flashed, there is no problem if it is the first time, but if it becomes a habit, the player in question will be given a warning.