In rock climbing, a whipper is an especially hard or dynamic fall where the rope is weighed by a significant load. A fall is considered hard when the climber falls beyond at least one piece of protection, which in trad climbing would mean the last placed cam or nut and in sport climbing would be the last successfully clipped quickdraw. The term 'whipper' comes from the whipping motion a climber will take if an unskilled belayer cuts the fall short, limiting the dynamic stretching nature of the rope and causing a pendulum effect (often into the wall). It has become ubiquitous, however, with a hard fall, regardless of whether the pendulum effect is achieved or not.
Whippers can be very dramatic falls, often for some distance. The distance of a whipper is determined by a number of factors, including rope stretch, any slack in the rope before the climber is ejected, and discrepancies in the relative weights between the climber and the belayer.
When a whipper is particularly long and the load great, a belayer will be lifted from the ground, occasionally all the way up to the first piece of protection or bolt. Depending on how far up the route the climber has gone, the climber may fall far enough to meet the belayer at an even level or even pass the belayer on the way down. This effect is known as teabagging in the rock climbing community, and is most common when a climber is significantly heavier than their belayer, but can happen in various other circumstances as well.
Dynamic rope is very well-suited to handle whippers, which can often be dramatically long and put a great deal of strain on a rope and equipment. Dynamic rope is rated by the UIAA to handle a specific number of whippers before being retired.