Glibbest is a superlative form of the word glib, which means speaking in a smooth, confident, and insincere manner. Some of the synonyms for glibbest are slick, smooth-talking, smooth operator, loquacious, voluble, articulate, fluent, persuasive, and facile. These words describe someone who is effortlessly able to express their ideas in a way that is both captivating and easy to understand. Glibness can be a positive trait in certain situations, such as when giving a persuasive speech, but it can also be viewed as negative if it is perceived as insincere or shallow. Overall, glibness can be a useful skill, but it is important to use it with honesty and authenticity.