Which word describes an optimistic demeanor that is often unrealistic?

The term that best describes an optimistic demeanor that tends to be unrealistic is "sanguine." This word originates from the Latin word "sanguis," meaning blood, and historically, it was associated with a cheerful disposition that was reflective of a healthy state. In modern usage, a sanguine individual is characterized by a hopeful and positive outlook, often in the face of difficulties, which can at times come across as overly idealistic or naive regarding the reality of situations.

Understanding the nuance of "sanguine" is crucial—especially in contexts where optimism appears disconnected from the real challenges being faced. This distinction makes it particularly suitable for describing someone who maintains a bright and buoyant demeanor even when circumstances might suggest a more cautious or sober approach.

In contrast, the other words do not carry the same connotation of unrealistic optimism. "Sententious" implies a pompous or moralizing tone; "saturnine" suggests a gloomy or melancholic disposition; and "satiate" refers to the state of being fully satisfied or filled, which does not pertain to attitude or optimism. Thus, "sanguine" stands out as the most fitting choice for depicting an optimistic demeanor that skews toward the unrealistic.