准儿 is a colloquial noun meaning 'certainty' or 'assurance' — used in spoken Chinese to talk about whether something is definite or dependable. It often appears in negative or interrogative patterns like 没准儿 ('not sure') and 有准儿吗？('is it certain?'). The character 儿 is a retroflex suffix that colors the pronunciation (r-colored final) and marks the word as informal.