The word "overwise" means excessively wise or intelligent, often to the point of being pretentious or arrogant. As such, there are several synonyms that can help convey this meaning effectively. These include words like know-it-all, pompous, conceited, haughty, overbearing, and arrogant. Other synonyms for "overwise" might include the terms vain, egotistical, superior, self-important, and big-headed. These words all convey a similar sense of pride and excessive self-confidence that can be off-putting to others. Ultimately, the choice of synonym will depend on the context and tone of the sentence where the word is being used.