An outside reversal occurs when the market closes above the previous day's high or below the previous day's low. If the NASDAQ Composite keeps trending down Thursday, it could qualify as a bearish outside reversal.
And that's not a good thing, according to Dennis Gartman, the commodities king.
"If you don't pay attention to outside reversal days, 85, 90 percent of the time you regret not having paid attention," he said on CNBC's "Power Lunch."
The NASDAQ was down almost 1 percent at just past 2:30 Thursday afternoon.
However, it doesn't necessarily mean this is the peak for the year, according to Gartman. It may just mean a five or 10 percent correction is coming, he said.
"But it is something that should be paid attention to, and if you don't, I'm certain you'll regret it," he said.
Gartman also said recent signs could mean money is moving out of equities and into plants and equipment, less liquid assets. But that's what should happen, he said, calling it "real economic activity."
He said broad commodity market indices making new highs could be signaling inflation rather than deflation, as many expect.
"The conversation was constantly about deflation," he said. "Instead, the commodities markets are starting to tell you that perhaps there's incipient inflation taking place."