In the sense a learner dictionary gives you, a mestizo is a person with one Hispanic parent and one Native American parent. In Spanish-speaking America, the older and wider use is a person of mixed Spanish and Indigenous American family — not always strictly 'one parent each', and not a casual word for anyone of mixed background. The word came into English from Spanish, and before that from Latin for 'mixed'. It belongs to a colonial ranking of people by blood, a system that tried to sort society into types. That history is not a small extra. It is why the word can feel heavy. In some places today people still use mestizo as a normal identity word. In others it sounds old, official, or like a label from outside. In the United States it is more a history or anthropology word than street talk. It does not mean 'Mexican', and it does not mean mixed-race in general. A person who is, say, Korean and German is not a mestizo. Spanish has mestiza for a woman; English sometimes keeps mestizo for all, and sometimes uses mestiza. Use the words people use for themselves when you know them.

梅斯蒂索（西班牙裔與美洲原住民的混血；不是泛稱所有混血）