in a blue moon

基本解释

From this perspective, unused functions should not be dropped from software merely because they are used once in a blue moon.
从这个观点来说，不习惯使用的功能不应该仅仅从软件中去除因为他们往往给使用他们的用户一种千载难逢的感觉。
To keep the game interesting, most of it is paid out in dribs and drabs: a machine that returned $95,000 of every $100,000 in one huge jackpot once in a blue moon would be too disheartening to play.
为了让赌戏保持吸引力，机器回馈的奖金都是零零碎碎的：如果在一回千载难逢的机遇下一次性返还奖池内10万美元的95%则太过令人沮丧，玩兴全无。
In English we say “once in a blue moon”.
“千载难逢”用英语我们说“once in a blue moon” 。
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Occasionally it will be hundreds of millions and once in a blue moon billions.
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And then, every once in a blue moon, something comes along that is in a category all its own.
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Once in a blue moon, he tells me, he saw an iPhone.
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