- a member of a upper-class family
- descent from nobility or royality
- an aristocrat
- a member of a rich, high up ancestry
- an individual of noble origin
- a person from a family that has a high social status
- The new student is very arrogant because he is a blue blood.
- Don't spend money like a blue blood rather save it for the future.
- I am not a blue blood can't afford this car I have to sell it.
- This restaurant is a perfect place to see the blue bloods of the city.
- A blue blood probably could never understand the pain of being homeless.
- Don't guess the status of this person by looking at his clothes. He is a blue blood of the city.
- She often tells her friends that she has blue blood flowing through her veins.
This idiom has actually been translated from the Spanish idiom "sangre azul". It was used in Spain for those aristocrats (people with high status) whose blood was considered pure. Or say that local people with pure Germanic genealogy who were not related to external invaders such as Moors, Jews, or other races. Compared to the dark-skinned Moors, their skin was so fair that blue veins showed clearly through their skin. At that time those people probably believed that their blood is not red but blue which gives them a different high up identity. And this is also true that the blue veins are visible in the white skin.
In the beginning of the 1800s, the idiom was translated into English.