A fake or counterfeit xWSS is a spaceship in a cellular automaton, other than Conway's Game of Life, that matches Life's lightweight, middleweight or heavyweight spaceship in at least one of its phases but evolves differently. Whereas the standard spaceships have period 4 and move orthogonally at c/2, fake xWSSes can have different periods and move in different directions at different speeds.
The c/2 orthogonal spaceship with the apgcode xq4_6frc in the non-totalistic rule B3/S23-ijn4a is a fake LWSS, despite matching the standard LWSS in all its phases, having the same period, and moving at the same speed:
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- Counterfeit Gliders (discussion thread) at the ConwayLife.com forums
- Rules with Mutant XWSSes (discussion thread) at the ConwayLife.com forums