aunt-in-law

noun4

1. •
   The wife of one's uncle or aunt (parent's sibling).

   • Between uncle and aunt-in-law, or uncle's wife, you have a connection of affinity, and you have the same between aunt and uncle-in-law, or aunt's wife. [sic] — 1871
2. •
   The aunt of one's spouse.
3. •
   The aunt of one's husband.

   • Petunia would later become an aunt-in-law to Harry's wife Ginevra Weasley and a great-aunt to Harry and Ginny's three children; James Sirius, Albus Severus, — 2009
4. •
   The aunt of one's wife.