The term rock in poker is used to describe a very tight player who rarely bets or bluffs with marginal poker hands. They only play the strongest preflop hands. A player who is a “rock” is the complete opposite of a “maniac” player. But, like maniacs, rocks can be very exploitable, as they stick with a rigid strategy.
Rock Poker Example:
A rock will only play strong hands, such as pocket aces, pocket kings, pocket queens, or AK. If a rock suddenly switches to a more aggressive play preflop or plays more loosely after the flop, turn, or river, high chances are that they have a big hand.