From Traderpedia

Definition: A sideways chart pattern between two converging trendlines in which the upper trendline is descending while the lower line is flat.

A Descending Triangle forms exactly the same way as it's cousin the Ascending triangle, only upside down and as part of a downward trend.

The converging trendlines this time comprise of a horizontal lower line, which indicates that the lowest current price is continually being hit. Where as the upper line this time is sloping downwards indicating lower highs on each candle. This pattern, being found in a downtrend, is regarded as Bearish.