What is the origin of the word conspiratorial?

The adjective comes from its related verb, conspire, "plot," or "make secret plans," from the Latin root conspirare, "to agree, unite, or plot," or literally, "to breathe together." Definitions of conspiratorial. adjective. relating to or characteristic of conspiracy or conspirators.

Is conspiratorial in the dictionary?

If someone does something such as speak or smile in a conspiratorial way, they do it in a way that suggests they are sharing a secret with someone.