Any of the unpaired fins in the midline of a fish’s body, i.e., a dorsal, anal, or caudal fin.
More example sentences
- But the first thing he saw as he surfaced was not a dolphin but the vertical fin of a great white.
- At hatching the larvae are quite advanced with pigmented eyes, well-developed jaws, digestive tracts, and vertical fin folds.
Definition of vertical fin in:
- The British & World English dictionary