King's Jaguar Step (3+4) crushing Heihachi's low attack (d/b+2) in Tekken 7.
The Crush System is a gameplay feature introduced in Tekken 5. From Tekken 5 onward, some moves are able to dodge, or crush, certain kinds of attacks during their execution. For example, in Tekken 7, Josie's Butterfly Edge can crush low attacks and also evade some mid attacks. Xiaoyu's Art of the Phoenix stance can crush high attacks and evade some mid attacks, and so on. Moves with crush properties are integral to the series' mix-up game as, depending on the move you dodge, well timed crush moves can deal guaranteed damage.
Crushing moves are not the same as simply evasive moves. For example, if a move high crushes, it means that it will dodge every high move in the game, even when the move can be seen touching the opponent.
Crushing moves are also known as Technical Crouch (TC) or crouch status (cs) moves when crushing highs, and Technical Jump (TJ) or jump status (js) moves when crushing lows.
This system is different from Tekken 7's Power Crush.