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1. dated slang A steel helmet worn by soldiers and military personnel during combat or in warzones. We learned the hard way during the war to wear your tin hat no matter what time of day or night it was.
2. slang By extension, any protective helmet, whether made of metal or not. Make sure you strap on your tin hat before getting on your motorcycle, OK?
3. slang A paranoid or delusional mindset centered around a belief in some conspiracy theory or another. (A shortened version of the more common term "tinfoil hat," referring to the cliché of using such headgear to prevent mind-control or having one's thoughts read.) A: "You know that they put those GPS trackers in your phones so the government can monitor you, right?" B: "Dude, you need to take your tin hat off and spend some time away from the Internet for a while." A lot people wearing tin hats believe the moon landing was faked by the US government.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
n. a soldier’s helmet. You use your tin hat for everything—washing, hauling water—you name it.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.