Your mother's sister is your aunt.
His relationship to you is brother-in-law.
cousin
Mom
In Hindi, you would call your mother's sister "mausi" or "masi".
Our cousins are our mothers sisters son :)
Mothers sister is aunt and son is cousin so daughter wouldn't that be a niece
Your mothers sister is your Aunt
A gatecrasher.
In Arabic, you would refer to your mother's sister as "خالة" (khala).
An Aunt.
Sister in law
Brother-in-law