Which term refers to something not openly practiced or engaged in?

The term "covert" refers to activities or practices that are concealed or not openly displayed. This aligns perfectly with the concept of something not being openly practiced or engaged in. Covert actions are typically characterized by secrecy, often to avoid detection or scrutiny. This can apply to various contexts, such as intelligence operations, private behaviors, or any action that is meant to be hidden from public view.

In contrast, the other terms do not convey the same meaning. "Convoluted" describes something that is complex and difficult to follow. "Compliant" refers to a willingness to conform or follow rules, which suggests transparency rather than concealment. "Credible" relates to the quality of being believable or trustworthy and does not inherently imply anything about openness or secrecy. Thus, the best choice for something that is not openly practiced or engaged in is "covert."