Alpha component in textures  says

An images alpha channel defines the parts of an image that are either visible (no alpha) or invisible (full alpha).

I interpret this as Alpha = 0x0 = fully solid, and 0xFF  = fully transparent

However, experimentally, i see that its reversed: A=0xFF produces solid, and 0x0 transparent.  :?

You're right, the wiki is incorrect.  Feel free to correct it.