[jamaksin]

What means "tinfoil" in this thread's usage, please?

[tcuoohjohn]

It is a reference to tin foil helmets. There is a phenomenon among very whacky conspiracy theorists that also leads them to believe that the government or aliens are sending " gamma" or other rays into their heads to prevent them from discovering " the real truth". The prevention measure is a cleverly crafted tin foil helmet to deflect the incoming rays.

There you have it...