day trading
n. Internet-based stock market trading in which individual investors quickly buy and sell equities to take advantage of short-term trends, and then sell most if not all of their holdings before the end of the day.
Other Forms
Examples
1999
As the go-go stock market keeps go-going, day trading looks powerfully seductive. 'Who wouldn't want to work at home in front of their computers and retire at 40?' says Philip Feigin, executive director of the North American Securities Administrators Association . . . The problem, he says, is that a deluge of largely unskeptical media coverage has so 'glamorized' day trading that people are ignoring its dangers. Fewer than one in 10 actually make money doing it, according to some experts. 'If you want to gamble,' Feigin advises, 'go to Las Vegas. The food is better.'
—Michael Meyers, “Fast, Yes. Easy? No.,” Newsweek, January 11, 1999
1999
Market reforms and access to the Internet have created a whole new breed of trader. Only an estimated 15,000 earn a living by day trading, but they are leaving their mark on the market.
—Jami Floyd, “Behind Internet mania,” ABC News, January 10, 1999
1996 (earliest)
Day trading is also attracting the analysis-driven baby boomers, says Paul D. Garverick, on-line editor of the Chicago-based American Association of Individual Investors.

"They are active researchers driven by the on-line services and the Internet," says Mr. Garverick. "They've discovered they can do pretty well on their own, so why take the risk of getting laid off?"
—Helen Bond, “Everyday investors can be their own brokers with stock-charting software and on-line market links,” The Dallas Morning News, February 27, 1996
Notes
The non-Internet version of the term day trading has been around for quite a while, with the OED showing an earliest citation from 1954 (and day trader from 1953).
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