gravitationally bound constellations

[Dazed and Confused]

I was going through the list of scientific principles here at G&S and came across the Pleiades's and Orion section were it stated that they are gravitationally bound constellations. I found a blurp on Wikipedia stating that Pleiades was gravitationally, but could find nothing directly relating to Orion. It did state that the Orion Nebula was gravitationally bound, but evidently this is not the same thing as the constellation of Orion. Any ideas?

[David Blacklock]

Unless I am mistaken, every item of mass in the universe affects all other mass in the universe, the amount of that affect being proportional to its amount of mass and inversely proportional (by some ratio) to the distance between it and any other piece of mass. That makes them both gravitational and no mass in the universe non-gravitational.

I'm open for correction

DB