To those involved in stock trading using Technical Analysis, a broadening pattern occurs when a security shows great movement with little direction. This pattern tends to take place in a stock that is showing increasing volatility while trending sideways for the most part. It's identified by a series of higher pivot highs and lower pivot lows, looking very similar to the inverse of a symmetrical triangle. A trendline drawn over the highs and under the lows makes the widening pattern.
Here's a visual example:
The Broadening Pattern is also referred to as a Megaphone or a Broadening Formation. By looking at the image I'm sure you can see why it is often times called a Megaphone.
The measuring implications of this pattern are somewhat controversial. The measured move is based on the width of the formation at the time of the most recent touch on the opposite end of the breakout. In this case there was a push below the lower line, which is bearish. The most recent touch on the opposite line was at approximately 267.50. The price where the lower line resided at the time of the 267.50 touch was approximately 250. This translates to a height of 17.50 (267.50-250) on this Megaphone. Therefore, the expected move after the bearish breakout of the pattern is 17.50 lower than the point of the breakout. The breakout took place at 242.50, so the target based on measurement should be 225.00.
Related terms: Ascending Triangle, Descending Triangle, Symmetrical Triangle