butterfly fish
noun
1
: any of a family (Chaetodontidae) of small brilliantly colored bony fishes of tropical seas with a narrow deep body and scaled fins
2
: a small brown freshwater bony fish (Pantodon buchholzi of the family Pantodontidae) of western Africa that has elongate winglike pectoral fins
Example Sentences
Recent Examples on the Web After lunch, Earle drifted through the museum, noting lava-lamp-like jellies, filigreed basket stars, and butterfly fish, which mate for life. 
Dana Goodyear, The New Yorker, 20 June 2022 It’s not uncommon to also see red pencil sea urchins, butterfly fish and moray eels. Sarah Sekula, USA TODAY, 23 Aug. 2020 During the dive, sea turtles—honu in Hawaiian—relax, swim nearby and enjoy a visit to butterfly fish and other reef fish that eat the algae off of their shells. Theresa Machemer, Smithsonian Magazine, 16 June 2020
Dana Goodyear, The New Yorker, 20 June 2022 It’s not uncommon to also see red pencil sea urchins, butterfly fish and moray eels. Sarah Sekula, USA TODAY, 23 Aug. 2020 During the dive, sea turtles—honu in Hawaiian—relax, swim nearby and enjoy a visit to butterfly fish and other reef fish that eat the algae off of their shells. Theresa Machemer, Smithsonian Magazine, 16 June 2020 Word History
First Known Use
1931, in the meaning defined at sense 2