How would you describe a "cryptic" message?

A "cryptic" message is characterized by its mysterious nature. This term refers to something that is deliberately vague, puzzling, or difficult to understand, often leaving the recipient unsure of its exact meaning. Cryptic messages can include coded language or be written in a way that conceals the true intent or information, prompting the reader to think deeply or decipher the underlying message.

In contrast, the other descriptions do not convey this quality of mystery. A message that is obvious would lack the intrigue and ambiguity typically associated with something cryptic. Similarly, while an intelligent message might display cleverness, it does not necessarily imply that the message is mysterious or hard to understand. An informal message suggests a relaxed tone and casual language, which is also at odds with the complexity and obscurity implied by the term "cryptic." Therefore, "mysterious" is the most fitting description for a cryptic message.