the.com/great aunt

means Your grandparent's sister — the sibling of one of your grandparents, a generation up and a branch over from your own great-uncle.

from A plain English compound that does exactly what it says. "Aunt" came into English through Anglo-Norman 'aunte', from Latin 'amita', a father's sister. "Great" here carries its old sense of "one further degree removed in kinship" — the same logic that gives us "great-grandfather." So a "great aunt" is literally an aunt at a greater generational distance, the prefix stacking up the family tree one rung at a time.