multisig

Definition

also multi-signature or multisignature; is a digital signature scheme which allows a group of users to sign a single piece of digital data.
Paraphrased by @henkvancann from Wikipedia source

KERI multi-signatures

The KERI team has conceptually chosen for minimal sufficient means and so-called dumb crypto: "'Dumb technology' is freely available, understandable to everyone and easy to implement. In our case: just hashes and digital signatures."

KERI has thresholded set of non-repudiable signatures.
KERI's CESR, and therefore KERI and ACDC is extensible with the latest more sophisticated multi-signature schemes like Schnorr signatures.