The term "most old-chestnut" refers to something that is outdated or overused. Its antonyms could be modern, fresh, trendy, innovative, or novel. These terms indicate a sense of originality and creativity, which are the opposite of being trite or hackneyed. For instance, a new spin on an old idea could be modern, while a completely new invention would be innovative. Additionally, up-to-date, contemporary, cutting-edge, or advanced are also antonyms for "most old-chestnut." These words describe something that is current and relevant, rather than outdated or cliche. Overall, using antonyms for "most old-chestnut" can add interest and excitement to your writing or conversation.