Aliasing stereoscopic -> stereogram.

Reason:

I wasn't initially in support of this, but after a little thought I now am.

Stereogram is much wider used, and even has a nice wiki entry for it. While they're technically (emphasis on technically) not the same thing, I feel like people will use the two tags interchangeably, so aliasing the lesser used one to the more proper, wider-used one is probably a good idea in the long run.

I think it breaks down into the same argument over gif + animated and while that isn't technically true, it's true enough times to warrant us aliasing them together