Anzaldua uses the word "mestiza" for meaning "caught between". Anzaldua is caught between the borderlands physically and spiritually. Her definition of the word mestiza can be somewhat similar to the OED definition. Many times a person of mixed races can feel caught between the two. They may have trouble figuring out which race they identify more with. This is similar to Anzaldua's definition of mestiza because the person is caught between two different cultures. The definitions are different because Anzaldua uses the word mestiza more as a feeling or state of mind rather than a description of an actual person.
The passage that conveys Anzaldua's meaning of the word "mestiza" the best is:
" The new mestiza copes by developing a tolerance for contradictions, a tolerance for ambiguity. She learns to be an Indian in Mexican culture, to be Mexican from an Angle point of view. She learns to juggle cultures. She has plural personality, she operates in a pluralistic mode - nothing is thrust out, the good the bad and the ugly, nothing rejected, nothing abandoned. Not only does she sustain contradictions, she turns the ambivalence into something else. "
This passage is a good definition of what the a mestiza is to Anzaldua. It shows that the mestiza is caught between two different cultures and has to accept the fact that she has to constantly change to fit in with those cultures.