If you describe something as unforgettable, you mean that it is, for example, extremely beautiful, enjoyable, or unusual, so that you remember it for a long time. You can also refer to extremely unpleasant things as unforgettable.
双语例句
例： A visit to the museum is an unforgettable experience.
参观这家博物馆是一次难忘的经历。
例： the outdoor activities that will make your holiday unforgettable.
将使你的假期难忘的户外活动。