Which term best describes someone as insincere in their communication?

The term that best describes someone as insincere in their communication is "disingenuous." This word is commonly used to indicate a lack of honesty or sincerity, suggesting that an individual might not be fully truthful or is concealing their true intentions. In the context of communication, a disingenuous person may employ flattery, exaggeration, or misleading rhetoric that appears to be genuine but truly is not. This term effectively captures the essence of a lack of authenticity in someone’s speech or behavior.

The other terms do not convey the same meaning. For instance, "replete" refers to being fully supplied or filled, which is unrelated to the nature of communication. "Pedantic" describes someone who is overly concerned with minor details or rules, often to the point of being dull or tedious, which does not imply insincerity. "Apposite" means relevant or appropriate, which is neutral in tone and does not address the issue of dishonesty or insincerity in communication. Hence, "disingenuous" is the most suitable choice for describing insincere communication.