brontosaurus
noun
bron·to·sau·rus ˌbrän-tə-ˈsȯr-əs 
variants or less commonly brontosaur
ˈbrän-tə-ˌsȯr
: any of a genus (Apatosaurus) of very large sauropod dinosaurs of the Late Jurassic : apatosaurus
Note: The name brontosaurus continues to be commonly used for these dinosaurs even though their former genus name (Brontosaurus) is considered invalid.
Example Sentences
Recent Examples on the Web Sauropods' species include the popularized brontosaurus and were known for their long necks and tails. 
Scott Gleeson, USA TODAY, 20 July 2022 On one side, there’s a T-rex that is 30 feet tall, on the other side is a brontosaurus that is 39 feet tall. Sheryl Devore, chicagotribune.com, 26 Apr. 2021 The latest attraction at the Volo Auto Museum is not a car — but a dinosaur, actually dozens of animatronic dinosaurs including a 30-foot-tall Tyrannosaurus rex and a 35-foot tall brontosaurus. Sheryl Devore, chicagotribune.com, 26 Apr. 2021 Ultimately, only two were built: a 45-foot-tall, 150-foot-long brontosaurus and a Tyrannosaurus rex named Mr. Rex. Los Angeles Times, 23 Mar. 2021 For years after the park closed, the skeleton of the Big Plunge towered over I-25 like the neck of a brontosaurus. Rachel Syme, The New Yorker, 10 Sep. 2020 Two full-figured men snacking on brontosaurus burgers, married to women with waists that are the same size as their necks. Katie Musgrave, refinery29.com, 20 May 2020 An orphaned brontosaurus teams up with other young dinosaurs in order to reunite with their families in a valley. Ben Flanagan | Bflanagan@al.com, al, 16 Mar. 2020 Trip skids across the floor at Hinkle Fieldhouse before games, finding his brontosaurus-sized bone and standing with it in front of the Butler bench seconds before tipoff. Gregg Doyel, Indianapolis Star, 22 Jan. 2020 See More
Scott Gleeson, USA TODAY, 20 July 2022 On one side, there’s a T-rex that is 30 feet tall, on the other side is a brontosaurus that is 39 feet tall. Sheryl Devore, chicagotribune.com, 26 Apr. 2021 The latest attraction at the Volo Auto Museum is not a car — but a dinosaur, actually dozens of animatronic dinosaurs including a 30-foot-tall Tyrannosaurus rex and a 35-foot tall brontosaurus. Sheryl Devore, chicagotribune.com, 26 Apr. 2021 Ultimately, only two were built: a 45-foot-tall, 150-foot-long brontosaurus and a Tyrannosaurus rex named Mr. Rex. Los Angeles Times, 23 Mar. 2021 For years after the park closed, the skeleton of the Big Plunge towered over I-25 like the neck of a brontosaurus. Rachel Syme, The New Yorker, 10 Sep. 2020 Two full-figured men snacking on brontosaurus burgers, married to women with waists that are the same size as their necks. Katie Musgrave, refinery29.com, 20 May 2020 An orphaned brontosaurus teams up with other young dinosaurs in order to reunite with their families in a valley. Ben Flanagan | Bflanagan@al.com, al, 16 Mar. 2020 Trip skids across the floor at Hinkle Fieldhouse before games, finding his brontosaurus-sized bone and standing with it in front of the Butler bench seconds before tipoff. Gregg Doyel, Indianapolis Star, 22 Jan. 2020 See More Word History
Etymology
New Latin, from Greek brontē thunder + sauros lizard; akin to Greek bremein to roar
First Known Use
1883, in the meaning defined above
Kids Definition
brontosaurus
noun
bron·to·sau·rus ˌbrän-tə-ˈsȯr-əs
: a huge plant-eating dinosaur with a long neck and tail and four thick legs