A few minutes after the Fed's 2 p.m. ET announcement, Cashin, UBS' director of floor operations at the NYSE, told CNBC's Bob Pisani that we "had a little bit of an up to the edge of the cliff moment there. We took out the morning lows, we took out the Monday lows in the S&P... and they had a stick save. They held exactly at 1770... That prompted some short covering here, which has brought us back."
If the S&P is unable to break through resistance at 1780 to 1783, Cashin said, "We may swoop back down the other way."
The S&P 500 stock index closed Wednesday at 1774.20, down 18.30.
Cashin believes the credit market's reaction indicates it doesn't think the Fed will continue to taper at its next meeting.
He'll be watching the currency markets overnight to see if there's "further spiraling."