Dolphin

noun

1. A carnivorous aquatic mammal in one of several families of order Cetacea, famed for its intelligence and occasional willingness to approach humans.
2. A fish, the mahi-mahi or dorado, Coryphaena hippurus, with a dorsal fin that runs the length of the body, also known for iridescent coloration.
3. A depiction of a fish, with a broad indented fin, usually embowed.
4. The dauphin, eldest son of the kings of France.
5. (history) A mass of iron or lead hung from the yardarm, in readiness to be dropped through the deck and the hull of an enemy's vessel to sink it.