Definition of porpoise
1
:any of a family (Phocoenidae) of small gregarious toothed whales;
especially
:a blunt-snouted usually dark gray whale (Phocoena phocoena) of the North Atlantic and North Pacific that typically ranges from 5 to 6 feet (1.5 to 1.8 meters) in length
2
:dolphin 1a(1)
—not used technically
Note:
While not closely related, porpoises and dolphins share a physical resemblance that often leads to misidentification. Porpoises typically have flat, spade-shaped teeth, triangular dorsal fins, and shortened beaks with relatively small mouths while dolphins have cone-shaped teeth, curved dorsal fins, and elongated beaks with larger mouths.
