Tin Foil Hat By EvilOctober 1, 2014February 25, 2020Popular Expression Tin Foil Hat = an aluminum hat believed to protect from outside forces (government etc.) controlling one’s mind. (Basically it means the person is crazy and paranoid.) Ex: John says aliens built the pyramids in Egypt. I guess he left his “tin foil hat” at home. Ex:You don’t believe in global warming? Where is your “tin foil hat?” You’re crazy! BACK to Popular Expressions