Dolphin (noun)

1. A small toothed whale with a curved dorsal fin and a slender beaklike snout.
2. A cetacean of the family Delphinidae, typically having a streamlined body and a curved dorsal fin.

Origin:

Middle english dolfin, from old french, from latin delphinus, from greek dolphingos.

Examples:

1. Dolphins are intelligent and social animals.
2. The dolphin swam gracefully in the water.
3. The dolphins are known to use tools and communicate with each other.
4. Dolphin watching is a popular tourist activity.
5. The dolphin exhibit at the aquarium is a popular attraction.