One of a group of young men who would carouse in taverns, then pick brawls on the street for entertainment. (noun)
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Use "roarer" in a sentence
"a thing we called a roarer; I don't know whether they have such things now."
"_Irishman_ (_discussing "roarer" recently purchased by P. - W.S. _)."
"_Whistling_ is only one of the variations of the sound emitted by a horse called a "roarer," and therefore needs no further notice, except to remind the reader that a whistling sound may be produced during an attack of severe sore throat or inflammation of the larynx, which passes away with the disease that causes it."