either of a pair of fins attached to the pelvic girdle in fishes that help control the direction of movement; correspond to hind limbs of a land vertebrate
例句
例句
Dorsal fin, tail fin and fat fins slightly yellow, pectoral fin, and ventralfin Tunqi gray.
背鳍、脂鳍和尾鳍稍带浅黄色,胸鳍、腹鳍和臀鳍灰白色。
The design is a nod to freshwater knifefish, which can move forward and backward, and hover, by rippling an elongated ventralfin.