A wallet requiring signatures from several keys before a transaction executes, expressed as a threshold such as three of five.
Why it matters
A multisig protects against any single key being compromised. It does not protect against every signer being shown the same misrepresentation of a transaction — a failure mode seen in more than one large custody incident.
Not advice. Definitions are for understanding, not instruction. Nothing here is financial, legal, tax or security advice.