I assumed the common meaning that would jump into the mind of any stockmarketfag:
In finance, a dead cat bounce is a small, brief recovery in the price of a declining stock.
A temporary recovery from a prolonged decline or bear market, followed by the continuation of the downtrend.
I assumed Q was applying it not to the stock market, but to the apparent success of the MSM in pushing their narrative in the past few days, the narrative of "White House in Disorder", security clearances taken away, people leaving, etc etc.
I could be all wrong though.