The term "third strings" typically refers to a position of lesser importance or skill. Antonyms for this term could include phrases such as "top tier," "main attraction," or "elite." Alternatively, words such as "beginner," "novice," or "rookie" could also serve as antonyms to "third strings." When referring to athletic or professional positions, antonyms could include words such as "star," "leader," "champion," or "captain." In social contexts, antonyms could include descriptors such as "popular," "influential," or "well-connected." Ultimately, the antonym for "third strings" depends on the context and the level of significance assigned to the role in question.