Indefinite pronouns in Japanese grammar refer to pronouns that do not specify a particular person, object, or quantity. These pronouns are used to express general ideas or concepts without limiting the conversation to specific instances. In Japanese, indefinite pronouns often come in pairs, with one indicating a positive concept and the other indicating a negative concept. Some common indefinite pronouns in Japanese include どこ (where), 何 (what), 誰 (who), and いつ (when). These pronouns play a significant role in everyday Japanese conversations, making it vital for language learners to understand their uses and meanings.