indecipherable

Not decipherable; impossible to decode, read, understand or comprehend.

The doctor's handwriting was indecipherable.

The second and third quarters of the shield are indecipherable on the stone but clearer in two other representations of the arms, a painted wooden funeral hatchment for Mary Davie[…]

Indistinguishable

The explanation some are suggesting is that the object takes on the appearance of what is behind it, or that it takes on the appearanec ^([sic]) of what the observer thinks is behind it. In both cases, the object is still visible. It's a visible representation of what's behind it, but it is still invisible, just indecipherable from its surroundings.

If you knew who Jerry was you'd swear you'd been cloned. Your posting style is virtually indecipherable from his.