fat finger syndrome / fat finger error
idiom

- to press the wrong button by accident when you are using a computer keyboard

(Cambridge Advanced Learner's Dictionary)

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A fat-finger error is a keyboard input error or mouse "misclick" in the the stock market or foreign exchange market whereby an order to buy or sell is placed of far greater size than intended, for the wrong stock or contract, at the wrong price, or with any number of other input errors.

Automated systems within trading houses may catch fat-finger errors before they reach the market or such orders may be cancelled before they can be fulfilled. The larger the order, the more likely it is to be cancelled, as it may be an order larger than the amount of stock available in the market.

Fat-finger errors are a product of the electronic processing of orders which requires details to be input using keyboards. Before trading was computerised, erroneous orders were known as "out-trades" which could be cancelled before proceeding.

Erroneous orders placed using computers may be harder or impossible to cancel. This was the case for UBS and 2001, when a trader sold 610,000 Dentsu-shares at ¥6, instead of 6 Dentsu-shares at ¥610,000. Even though the error was spotted immediately, the Tokyo Stock Exchange did not cancel the trades and UBS had to buy back the shares at market-value which caused them a loss of US$100m.


Sources:

"Trader's slip leaves UBS Warburg £71m poorer". The Daily Telegraph

"Fat Finger Error". Investopedia.

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Practice OWAD in a conversation today, say something like:

"Do you think that speech recognition and strong AI will eventually eliminate FAT FINGER ERRORS?"