What does "brother-in-law" mean?

A male relative of one's generation, separated by one degree of marriage:; The brother of one's spouse.

How do you pronounce "brother-in-law"?

Pronounced //ˈbɹʌðɚ ɪn ˌlɔ//.

//ˈbɹʌðɚ ɪn ˌlɔ// noun

noun ·Rare ·Advanced level

Noun

1
A male relative of one's generation, separated by one degree of marriage:; The brother of one's spouse.
"The US Securities and Exchange Commission has closed its insider trading investigation into stock trades made by then-Sen. Richard Burr and his brother-in-law at the outset of the pandemic, the former senator announced Friday."
2
a brother by marriage wordnet
3
A male relative of one's generation, separated by one degree of marriage:; The husband of one's sibling.
4
Co-brother-in-law: A male relative of one's generation, separated by two degrees of marriage:; The husband of the sibling of one's spouse.
"He was appalled by trench conditions and the prolongation of the war, a disillusionment further encouraged by the Easter rising, in which his brother-in-law, Francis Sheehy-Skeffington (qv), was murdered by a deranged Anglo–Irish officer, J. C. Bowen-Colthurst (qv)."
5
Co-brother-in-law: A male relative of one's generation, separated by two degrees of marriage:; The brother of the spouse of one's sibling. uncommon

"My brother-in-law is ready to lose his temper at trifles."

From Middle English brother-in-lawe; equivalent to brother + -in-law.

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.