Wikipedia definition
1. Mottainaiis a Japanese term meaning "a sense of regret concerning waste when the intrinsic value of an object or resource is not properly utilized". The expression "Mottainai!" can be uttered alone as an exclamation when something useful, such as food or time, is wasted, meaning roughly "Oh, what a waste!" In addition to its primary sense of "wasteful", the word is also used to mean "impious; irreverent" or "more than one deserves".
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Read “もったいない” on Japanese Wikipedia
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