1. A method, skill, or procedure that is not known, recognized, or familiar to a person or group
The magician used an unknown technique to make the rabbit disappear.
O mágico usou uma técnica desconhecida para fazer o coelho desaparecer.
2. A specialized approach or method whose origin, creator, or details are not documented or understood
Scientists are studying this unknown technique used in ancient construction.
Cientistas estão estudando essa técnica desconhecida usada na construção antiga.