Bull trap
In stock market trading, a bull trap is an inaccurate signal that shows a decreasing trend in a stock or index has reversed and is now heading upwards, when in fact, the security will continue to decline.
It is seen as a trap because the bullish investor purchases the stock, thinking it will increase in value, but is trapped with a poor performing stock whose value is still falling.
See also
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References

Look up bull trap in Wiktionary, the free dictionary.