Extremely good, or extremely big and impressive — a playful way of saying 'even better than super'. The 'duper' half means nothing at all; it is there only because it rhymes, the same trick English plays in 'okey-dokey' or 'easy-peasy'. That rhyme is the whole flavour of the word: it is light, childish, and cheerful. Adults use it with children, or with each other when they are being deliberately silly, or — very often — sarcastically, in a flat voice, to mean the opposite: 'Oh, super-duper, another meeting.' It usually sits before a noun ('a super-duper new phone') or before another adjective ('super-duper expensive'). It is not a word for essays, business emails, or exams. You will see it written super-duper with a hyphen, superduper, or super duper; the hyphen is the most common. Because it sounds dated to some younger speakers, it can carry a hint of 'the way my dad talks'.

超級棒的、頂呱呱的（俏皮、帶點孩子氣的說法，也常用來反諷；正式場合不用）