ventral fin
noun
1- Zoology another term for PELVIC FIN.【动】同PELVIC FIN.
1.1
- an unpaired fin on the underside of certain fishes（某些鱼类下腹的）腹鳍。
1.2
- a single vertical fin under the fuselage or tail of an aircraft（飞机机身或机尾下的）垂直翼。