Which term describes behavior that is boisterous and noisily aggressive?

The term that best describes behavior that is boisterous and noisily aggressive is "obstreperous." This adjective conveys a sense of unruly, loud, and difficult-to-control behavior, often characterized by a lack of restraint or adherence to social norms. Obstrepereousness is typically associated with being disruptive or confrontational, which aligns perfectly with the idea of being aggressively noisy.

The other options do not capture this meaning effectively. A pacifist represents someone who opposes violence and war, suggesting a peaceful demeanor rather than an aggressive one. Timid reflects shyness or a lack of confidence, which is the opposite of being boisterous or aggressive. Reserved indicates a person who is more restrained and does not exhibit overtly bold or aggressive behavior. Hence, "obstreperous" is the most fitting term in this context.