Art Cashin, UBS director of floor operations at the NYSE, said stocks are selling off due to a pretty bad backdrop.
He pointed to concerns about ISIS and Ebola, the breakup of the AbbVie-Shire deal and weakness in Greece as dragging down major averages.
"We were set up for a negative opening anyway," Cashin said. "Then at 8:30 [a.m. EDT], we got absolutely dreadful economic data and that kind of compounded everything." Retail sales, producer prices and New York manufacturing reports all disappointed.
Stocks dropped, rebounded, then dropped again during the trading day with the approaching correction territory, which is a pullback of 10 percent or more from a recent high. The Nasdaq Composite and Russell 2000 are already in correction territory, down 10 and 11 percent from their respective highs.
Read MoreOPEC creating price war: Oil trader
Cashin warned if West Texas Intermediate crude oil (WTI) drops below $80, stocks could see another wave of selling. WTI slid as low at $80.01 in Wednesday's trade, putting it at a two-year low.
Oil does not normally drive the stock market; however, overall concerns about deflation, or falling prices, and a rising U.S. dollar are among the biggest factors pressuring stocks in the past several weeks.
—By CNBC's Kristen Scholer