A sister-in-law of one's mother; the wife or ex-wife of a maternal uncle.
A sister of one's mother.
A similar great aunt, etc.
A person who shares a parent; one's brother or sister who one shares a parent with.
A node in a data structure that shares its parent with another node.
The most closely related species, or one of several most closely related species when none can be determined to be more closely related.