"To confirm an uptrend" means to verify or validate that a particular trend in the stock market or any other trading market is moving upwards or rising. Full definition
Market in confirmed uptrend following a shift toward institutional buying (accumulation) and many leading stocks breaking out of chart patterns. (aaii.com)
Lastly, there is confirmation, in the lower section of the chart, by virtue of the climb since the divergence indicator became positive, confirming the uptrend on 3rd October, the day Bitcoin prices started the climb. (links2exchange.net)
Additionally, per Bill McBride a / k / a Calculated Risk, there is a strong leading relationship between housing starts and the unemployment rate, so a confirmed uptrend should mean a reduction in the unemployment rate. (businessinsider.com)