Ungenuine, a term used to describe something that lacks authenticity or sincerity, can have several antonyms depending on the context. If we wish to express the opposite of ungenuine, we can use terms like genuine, sincere, real, honest, or authentic. These words indicate a sense of truthfulness and integrity that the term ungenuine lacks. Expressions like insincere, fake, artificial, or phony can also serve as antonyms for the term ungenuine. In essence, any term that represents honesty, truthfulness, and genuineness can be considered an antonym for ungenuine.