A Swing High is a "peak" identified within a series of bars or within an indicator or oscillator. A Swing High consists of two "legs", and starts with an initial up leg which is then followed by a down leg. A leg is defined as two or more bars going in any one direction. For example, when two or more consecutive bars produce higher (bar) highs and higher (bar) lows. In this instance, the smallest possible up leg would have developed. Inversely, to have a down leg you need no fewer than two bars showing lower (bar) highs and lower (bar) lows. When an up leg is followed by a down leg, the "peak" that is created is considered a Swing High.
Background: A Swing High starts its life out as a pivot high consisting of a lower high to the left and right of a price bar. To additionally produce a formal Swing High requires that the bar forming the price high has two bars with lower highs preceding it and two bars with lower highs following it.
Swing Highs can act as an area of support or resistance.
Practical Use: Defining a Swing High is helpful to technical analysts because many trendlines are drawn connecting the peaks of Swing Highs to each other. This is also helpful to begin gaining a deeper understanding of the sentiment read of a chart.