What does tinfoil mean?
Tinfoil is a thin, flexible sheet of metal used chiefly for wrapping and lining objects. Although the word contains tin, modern household foil is often aluminum rather than tin. Tinfoil also denotes, informally and often humorously, a hat made from such foil—most famously the pointed “tinfoil hat” associated with conspiracy theories and jokes about secret or impractical schemes. The adjective tinfoil describes something made from, covered with, or resembling that sheet, and is used chiefly before a noun. As a verb, tinfoil means to cover or wrap with foil, though this use is uncommon. The expression “tin foil” remains common and may be written as two words. Tinfoil is familiar in both British and American English, though material and spelling conventions can vary. It combines a precise household reference with a memorable image of eccentricity and conspiracy.
A thin, flexible sheet of metal foil, traditionally tin but now often aluminum, used for wrapping or lining objects; informally, a hat made from such foil.
"The electrician used tinfoil to form a simple reflector."
The material sense is usually uncountable. The informal hat sense often carries a humorous or dismissive connotation.
To cover, wrap, or line something with tinfoil.
"They tinfoiled the components to protect them from the elements."
This is an uncommon usage and can sound technical, playful, or jocular.
Made of, covered with, or resembling tinfoil.
"The model aircraft had tinfoil wings."
Chiefly used before a noun.
Usually uncountable when referring to the material generally; the plural can refer to separate sheets or pieces.
"We used two tinfoils to cover the trays."
The tin in tinfoil is often more historical than literal: most household foil today is aluminum, yet the metal hat that symbolizes wild theories still shines.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of tinfoil
Tinfoil developed from the expression tin foil and was eventually written as one word. Tin is an old Germanic word in English, while foil comes through French from Latin folium, meaning “leaf.” The compound originally referred to foil made of tin, although modern household foil is commonly made from aluminum.
Related word forms
How tinfoil is actually used
The word is standard in both British and American English. The verb is uncommon and tends to sound technical, playful, or jocular, while the adjective is chiefly used attributively.
Easily confused with tinfoil
Tin is the metal itself, whereas tinfoil is a thin sheet made from metal and, informally, a hat made from it.