The thumbs-up signal is considered an insult in Iran, where this is called a bilakh and roughly translates to "up yours." The OK sign, where thumb and forefinger meet to create a circle, is an obscene gesture if you're in Brazil or Turkey, where you're comparing someone to a particularly dirty part of the body. And if you're motioning to someone in Latin America by using an upward palm and waving your fingers back, you might get a much friendlier response that anticipated, as this is a common romantic solicitation.

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