From Traderpedia

Definition: A chart pattern similar to the flag, except that it is more horizontal and resembles a small symmetrical triangle.

This is a sister pattern to the Flag and again is a continuation pattern. The Pennant is very similar to the Flag except that it moves horizontally to give the appearance of a small ascending triangle.

It too indicates a point where the stock or index is 'resting' or consolidating before it breaks out and continues with its prior trend.

Just as with the Flag, the Pennant can be formed in either an uptrend or a downtrend. The image above shows it in an uptrend. In a downtrend it would form exactly the same except flipped upside down and the signal for a 'buy' would become a signal for a 'sell'.