- any of several small, gregarious cetaceans of the genus Phocoena, usually blackish above and paler beneath, and having a blunt, rounded snout, especially the common porpoise, P. phocoena, of both the North Atlantic and Pacific.
- any of several other small cetaceans, as the common dolphin, Delphinus delphis.
- (of a speeding motorboat) to leap clear of the water after striking a wave.
- (of a torpedo) to appear above the surface of the water.
- to move forward with a rising and falling motion in the manner of a porpoise: The car has a tendency to porpoise when overloaded.
Origin of porpoise
- any of various small cetacean mammals of the genus Phocaena and related genera, having a blunt snout and many teeth: family Delphinidae (or Phocaenidae)
- (not in technical use) any of various related cetaceans, esp the dolphin
Word Origin and History for porpoising
The Old French word probably is a loan-translation of a Germanic word meaning literally "sea-hog, mere-swine;" cf. Old Norse mar-svin, Old High German meri-swin, Middle Dutch mereswijn "porpoise" (the last of which also was borrowed directly into French and became Modern French marsouin).
Classical Latin had a similar name, porculus marinus (in Pliny), and the notion behind the name likely is a fancied resemblance of the snout to that of a pig.