Which term refers to something that is secret or hidden?

The term "covert" is used to describe something that is secretive, hidden, or not openly acknowledged. In various contexts, such as military operations or intelligence gathering, "covert" actions are carried out without public knowledge or visibility, emphasizing their concealed nature.

In contrast, the other terms do not convey the same meaning of secrecy. "Open" refers to something that is accessible or visible to all, while "obvious" indicates something that is clear or evident, easily perceived by others. "Direct" implies a straightforward approach that lacks ambiguity or concealment. Therefore, "covert" is the term that aligns with the idea of being secret or hidden.