The antonyms for the word "more infantine" can be words such as adult, mature, sophisticated, intelligent, experienced, and knowledgeable. While "more infantine" means childlike, immature, innocent, and inexperienced, its antonyms describe people who have grown up and become more worldly-wise. Someone who is "more infantine" lacks the understanding of the complexities of life, while an adult is capable of handling life's challenges. Being "more infantine" can also imply a lack of skill, while being mature and experienced means having mastered a skill set. In short, the antonyms of "more infantine" highlight the qualities of an adult who has endured the trials of life and learned from them.