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

It requires little effort to arrange the group’s most unhinged statements into a cornucopia of lunacy, surpassed in recent memory only by the tinfoil conspiracism of QAnon.

From Salon • Jan. 20, 2026

A large roll of non-stick tinfoil couldn't hold a candle to Mamma Mia actress Amanda Seyfried, who wore a shiny metallic gown featuring flower appliques.

From BBC • May 6, 2024

Perhaps in the future, conspiracy theorists with tinfoil hats won’t seem so crazy after all.

From Slate • Mar. 25, 2023

Zafoona rolled back the tinfoil and eyed the fillet of fish lying on a small pile of yellow rice.

From "Shooting Kabul" by N. H. Senzai