What does "co-sister-in-law" mean?

One's spouse's sister-in-law, especially one's husband's brother's wife, one's brother's wife in relation to the spouses of his siblings; either of two (or more) women who are married to brothers, in relation to the other.

What is a synonym for "co-sister-in-law"?

Common synonyms include: co-aunt, co-sister.

Co-sister-in-law

noun

noun ·Rare ·Advanced level

Definitions

Noun

1
One's spouse's sister-in-law, especially one's husband's brother's wife, one's brother's wife in relation to the spouses of his siblings; either of two (or more) women who are married to brothers, in relation to the other.
"[The Russian word] Yátrov', for the husband's brother's wife or co-sister-in-law, so diagnostic a status within the patrilocal household, has passed entirely out of the language."
2
One's brother-in-law or sister-in-law's sister; one's sibling's spouse's sister; either of two (or more) women whose siblings are married, in relation to the other.

Synonyms

All synonyms

co-aunt co-sister

Example

More examples

"[The Russian word] Yátrov', for the husband's brother's wife or co-sister-in-law, so diagnostic a status within the patrilocal household, has passed entirely out of the language."

Etymology

From co- + sister-in-law or co-sister + -in-law.

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