The stock AAPL, +3.63%  climbed 2.2% in midday trade, but it was still down 15% since July 22. That's when its 50-day moving average ("MA"), which chart watchers use as a guide to the short-term trend, started turning lower.

The 50-day MA is at $121.2497, according to FactSet, crossing below the 200-day MA, which slipped to $121.5105. Many use the 200-day MA as a dividing line between long-term uptrends and downtrends.

Don't miss the slide show: "A death cross in Apple's stock is coming."

When the 50-day MA crosses below the 200-day MA, it's known to chart watchers as a "death cross." Many of them see that as marking the spot where a short-term decline turns into a longer-term downtrend.

Apple's last death cross appeared on Dec. 7, 2012, when the stock closed at $76.18 on a split-adjusted basis. The stock fell another 27% before hitting bottom on April 19, 2013.