In the context of Tai Chi, if someone is NOT in a good stance (ala off balance) when they are HIT... then they can be thrown back with a Strike OR a Push.
Basic example: "Press" in Tai Chi can be used as a Strike, a Push or steady pressure. Depends on how violent you want it to be. But it will not make a guy fly back if you attack straight into his power.
If I
yield and make my opponant stumble slightly forward and I HIT (or strike or push) him at a line perpendicular to where his feet are on the floor...ala his weakest angle. He can easily be made to fly backwards.
This was the question at hand: Taiji 1983 asked about a GOOD STANCE. I was telling him NOT to attack in that power line. It's common Tai Chi Theory.