A pattern characterized by a series of three peaks, the first and third being lower than the middle. Volume, heavy on the first peak, declines on the next two. Completion is marked by the breaking of the "neckline" (an extension of the line connecting the troughs between the three peaks) accompanied by heavy volume. An inverse head and shoulders is the same pattern upside down and volume increases through the pattern.
A well-known reversal pattern marked by three (or more) prominent peaks with a middle peak (the head) that is higher than the other peaks (the shoulders). When the trendline (neckline) connecting the troughs at the bottom of the pattern is broken, the pattern is complete.