A rumpus is an uproar or a commotion. Setting a litter of excited puppies loose in a kindergarten classroom would be sure to cause a rumpus.
While a rumpus can be loud and boisterous, like the rumpus underneath a piñata in the midst of a huge birthday party, others take the form of heated arguments. This kind of rumpus might occur during a political scandal, for example. Experts guess that the informal rumpus might come from the now-obsolete word robustious, which means "boisterous or noisy." In the mid-twentieth century, children's playrooms began to be called "rumpus rooms."