They were shit-talking each other in the locker room, complaining about each other's performance.

shit 原意是"粪便"，在俚语中常用来表示"糟糕的、讨厌的"事物。 talking 是动词 talk 的现在分词形式，意思是"说话、谈论"。 shit-talking 是一个俚语短语，指"说坏话、恶意批评"，通常是在背后贬低或诋毁他人。