1. Infrastructure, mechanical, or technological systems that are hidden from view, typically built into walls, ceilings, or underground
The building features concealed systems for HVAC and electrical wiring.
O edifício possui sistemas ocultos para HVAC e fiação elétrica.
2. Hidden or covert operational procedures or networks
The intelligence agency maintained concealed systems for encrypted communications.
A agência de inteligência mantinha sistemas ocultos para comunicações criptografadas.