4 definitions
Straight definitionupdates Descartes's evil demon; Hilary Putnam, 1981
The meaning, not a take.com
Brain in a vat (n.) is a thought experiment asking how you could know you are not a brain fed false experiences by a computer.
Definition.com
A Brain in a vat (n.) is "what if none of this is real, man" with footnotes.
Definition.com
A Brain in a vat (n.) would feel exactly as sure as you do right now that it isn't one.
Definition.com
A Brain in a vat (n.) is unanswerable, and everyone who hears it still goes to lunch.