brother-in-law
noun
broth·er-in-law ˈbrə-t͟hər-ən-ˌlȯ 
ˈbrət͟h-rən-,
ˈbrə-t͟hərn-
plural brothers-in-law ˈbrə-t͟hərz-ən-
1
: the brother of one's spouse
2
a
: the husband of one's sibling
b
: the husband of one's spouse's sibling
Word History
First Known Use
14th century, in the meaning defined at sense 1
Kids Definition
brother-in-law
noun
broth·er-in-law
ˈbrə-t͟hər-ən-ˌlȯ
plural brothers-in-law
1
: the brother of a person's spouse
2
: the husband of a person's sibling
3
the husband of a person's spouse's sibling