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English definition of “you can't judge a book by its cover”

you can't judge a book by its cover

said to show that you cannot know what something or someone is like by looking only at their appearanceSeeming and purporting to beFaking and pretending
(Definition of you can't judge a book by its cover from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)

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to direct the way that a ship, aircraft, etc. will travel, or to find a direction across, along, or over an area of water or land, often by using a map

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