tinfoil

American  

[tin-foil] / ˈtɪnˌfɔɪl /

noun

1. tin, or an alloy of tin and lead, in the form of a thin sheet, much used as a wrapping for drugs, foods, tobacco, etc.

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tinfoil British  

/ ˈtɪnˌfɔɪl /

noun

1. thin foil made of tin or an alloy of tin and lead

2. thin foil made of aluminium; used for wrapping foodstuffs

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Usage

What is a tinfoil hat? Tinfoil hat is a shorthand for saying someone believes in conspiracy theories, is paranoid, or is crazy more generally.

Etymology

Origin of tinfoil

First recorded in 1425–75, tinfoil is from the late Middle English word tynfoile. See tin, foil ²

Example Sentences

He was a 25-year-old tinkering with self-tanners, but all the intrigue and action seemed to be around the lab next door, with its strange music, flashing lights and tinfoil covering the porthole.

From The Wall Street Journal • Mar. 18, 2026

During Monday’s hearing, he complained that mainstream news media, including the Washington Post, had portrayed him and his allies “like we have a tinfoil hat on our heads.”

From Slate • Dec. 19, 2025

One suspect had an expensive phone wrapped in tinfoil in an attempt to block the device's signal and avoid it being traced.

From BBC • Dec. 12, 2024

So I went to my hair cutter and had him do it, with the tinfoil and everything.

From Los Angeles Times • May 28, 2024

Somkit pointed to the tinfoil cones cupped around the lights.

From "A Wish in the Dark" by Christina Soontornvat