The phrase "in secret" refers to something that is done or kept hidden from others. There are several other ways to express this idea using alternative words and phrases. "Covertly" describes actions that are done secretly and in a discreet manner. "Clandestinely" emphasizes the idea of doing something in secrecy with the intention of avoiding detection. "Privately" suggests that something is hidden from others for personal reasons, while "confidentially" implies that information is shared in strict confidence and not meant to be disclosed publicly. Other synonyms include "under wraps," "behind closed doors," and "in the dark".