Your cousin
The child of your mother's sister is your first cousin.
Your child would call your sister her aunt.Your sister would call your child her niece or nephew depending on gender.Your sister's children would call your child their cousin.
cousin
Mom
In Hindi, you would call your mother's sister "mausi" or "masi".
Our cousins are our mothers sisters son :)
His relationship to you is brother-in-law.
bessy
Your mothers sister is your Aunt
Mothers sister is aunt and son is cousin so daughter wouldn't that be a niece
A gatecrasher.
In Arabic, you would refer to your mother's sister as "خالة" (khala).