A flash mob is a group of people who come together suddenly in a public place, do something unusual for a short period of time, and then quickly break up.

快闪族，是指一群人突然在公共场所聚集，在短时间内做一些不寻常的事情，然后迅速散开。

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Alternating between physical and mental activities helps, too, as does increasing the novelty of lessons by blending films, tapes, flash CARDS, and group work.

脑力和体力活动的交替进行也颇为有效，例如课堂上放电影、磁带、教学卡片，以及让孩子加入小组活动等。

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This particular one is a large-screen LCD suitable for viewing by a research group or class, with built-in media player, Web browser, Flash player, and so on.

这个特定的产品是适合于研究组或者班级使用的大屏幕 LCD，并且拥有内置的媒体播放器、Web 浏览器、Flash 播放器等等。

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In New York, a group of dancers staged a "flash-mobbing" in Times Square.

BBC: 'Space clown' hosts global show

Flash Mob America, which stages events at corporate conferences and trade shows, began in 2009 after a group of friends put on a flash-mob tribute to Michael Jackson, which went viral.

WSJ: Spontaneity for Hire: Flash Mobs Go Corporate

Critics say flash orders give a select group of high-speed traders a window into the direction of the market, giving them the ability to trade at lightning speeds ahead of less fleet-footed investors.

WSJ: Ban on Flash Orders Is Considered by SEC