A vessel (especially a paddle steamer) propelled by a pair of paddle wheels positioned one on each side(noun)
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Use "sidewheeler" in a sentence
"I love the look of a classic antebellum steamboat, and the artist here actually got it right and gave me a sidewheeler, not a sternwheeler."
"There was also an armed sidewheeler at point C and also point E on the map above – with some serious high caliber guns."
"Jim pointed out that many ships plied the waters 50 years ago, including the SS District of Columbia, which made overnight trips to Norfolk, and an ex-Hudson River sidewheeler named the SS Bear Mountain."