Obstreperous is a formal word that describes people or things that stubbornly resist control; in this use it’s a synonym of unruly. A person or thing described as obstreperous may also be defiantly or aggressively noisy.

// The moment the paper airplane landed, the instructor addressed the unruly class, telling them in the harshest tone that obstreperous conduct would not be tolerated.

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“In the 1887 essay ‘Silent People as Misjudged by the Noisy,’ an Atlantic contributor proposed an economical approach to talking: ‘As we get on in life past the period of obstreperous youth, we incline to talk less and write less, especially on the topics which we have most at heart,’ the writer noted. ‘We are beginning to realize the uselessness of perpetually talking … If there is a thing to be said, we prefer to wait and say it only when and where it will hit something or somebody.’” — Isabel Fattal, The Atlantic, 17 Feb. 2024

Imagine walking a dog down a sidewalk in a neighborhood full of delicious smells and other temptations—it’s easy to picture your pooch barking and straining at the leash to chase a squirrel, or dragging you toward something enticingly (to them) stinky, right? But can you imagine saying to your doggo in response, “Quit being so obstreperous!” Probably not. Obstreperous has a much more formal flair than words, such as stubborn or unruly, used to describe similar behavior. As such it’s unlikely to be used in casual speech or contexts like the one above. The word comes from a combination of the handy Latin prefix ob- (meaning “against”) and strepere, a verb meaning “to make a noise”; someone who is obstreperous can be thought of as literally making noise to rebel against something, much like a protesting crowd or an unruly child. Strepere has made little noise in the English lexicon, however; in addition to obstreperous it seems only to have contributed to the rarely encountered strepitous and its synonym strepitant, which mean “characterized or accompanied by much noise”—that is, “noisy.”