second dorsal fin
/ˈsɜːtʃandɹˈɛskjuː antˈɛnəz/
n
English · second dorsal fin中文 · 第二背鳍Español · aleta dorsal posteriorFrançais · seconde nageoire dorsale
意味：Swimming appendage formed of a membrane and rays located on the middle posterior dorsal portion of the body; it provides stability.