Not certain or reliable; indefinite or unclear, often referring to information, memories, or facts.
その日の出来事については記憶が不確かだ。
My memory of what happened that day is uncertain.
情報源が不確かなので、もう一度確認してください。
The source of the information is unreliable, so please check again.
彼の説明は不確かで納得できなかった。
His explanation was unclear and unconvincing.