Pecksniff is a term that is often used to refer to someone who is insincere or hypocritical in their actions or behavior. Thankfully, there are plenty of synonyms that can be used to describe such a person. Some good options might include phony, two-faced, deceitful, disingenuous, duplicitous, false, insincere, or hypocritical. Other possible synonyms for pecksniff might include treacherous, backstabbing, conniving, or calculating. Ultimately, the best synonym for pecksniff will depend on the specific situation and context in which the term is being used, so it's wise to carefully consider the options before settling on a particular word.