Is there a name for it? Cause “brother-in-law’s wife” is really really long. Is she your sister-in-law?
Could be your sister also?
Assuming you mean the wife of your spouse’s brother. She is your spouse’s sister-in-law. There is no simple term to describe her relationship to you. I suppose you could refer to her as your sister-in-law even though that’s not really correct.
“Brother-in-law’s wife” is not *really *all that long 
(My wife had a relative visiting us a few weeks ago and she called her her niece. When I asked how she was related, it took a couple of minutes to explain it all. She wasn’t really her niece, and the relationship jumped across two marriages, etc.)
Technically there is no lrgal relationship. In many areas, however, two couples of wshich one spouse each are siblings regard each other as in-laws, so that Sam, who is married to Mary, who is Jane’s sister, regards Jane’s husband Bill as his brother-in-law, even though there is no legal connection.
I did a doubletake at jonbvn’s post, thinking at first he was speaking of the couples comprised of siblings phenomenon: Bill and Bob, who area brothers, marry sisters Sally and Sue respaectively, so that both aunt and uncle are blood realatives to the children of either couple (who are themselves double cousins to the children of the other couple). Then I realized he was pointing out that a ‘brother-in-law’ may be descriptive of your sister’s husband.
I believe the term you are looking for is “none”.
I still call that one sister-in-law. Because you share the same parents-in-law. I don’t regard my interpretation as more or less valid than anyone elses because, ironically, there is no law about it. But it makes sense to me, having attended family gatherings with several of those relationships present.
In my family, a brother-in-law’s wife is called a sister-in-law. You could refer to a visit by the couple as “My brother- and sister-in-law came over for dinner on Friday night”, although it’s really hard to vocalise that hanging hyphen. XD
I love English but we really need to steal some more words from other languages, especially relationships. In Hindi your husband’s elder brother is your “Jhet”, and his wife is your “Jhetani”; his younger brother is your “Devur”, and his wife is “Devrani”.
Come on, English! I’m sure we can beat up some language and steal their words!
The thing is, too, is there is a relationship, even if there is no “real” one - there are only two sons, and (presumably) there are only two daughters-in-law - me and her. So there should be something. Jhetani!
In Spanish we call that “concuñada”; a poll taken by a bunch of Hispanics asking Anglos in Miami brought up that there doesn’t seem to be a specific term in English.
Spouses are cónyuges; parents-in-law are suegros and parents of spouses are consuegros; siblings-in-law are cuñados and siblings of spouses are concuñados - the “con” means “with.”
?? The parent of my spouse is my parent-in-law - that’s the definition. I don’t follow the distinction you’re making here.
I do this, too … at least around here, it’s common usage.
It’s not so much a linguistic phenomenon as it is a sociological or anthropological one. Evidently, there are six basic systems. English speakers use “Eskimo kinship.”
I’m pretty sure she meant to say “spouses of parents,” not “parents of spouses.”
Or, you can change frame of reference (which happens when you have children) and just say (the kids’)“Aunt Kathy”.
FWIW I looked up possible English translations for the German equivalent term Schwippschwager (n,m)/Schwippschwägerin (n,f) [this term covers a sibling’s spouse’s sibling as well as a spouse’s sibling’s spouse] but the German-English dictionaries I consulted only had circumlocutions, so this also argues for there being no English term.
If you and I marry, my parents and your parents are “consuegros” to each other.
Ah, thank you. The “to each other” is what I didn’t grasp.
Another vote for sister-in-law.
English doesn’t even have words to differentiate my sister’s husband (brother-in-law) from my spouse’s brother (brother-in-law).
As far as I’ve ever known, my brother-in-law’s wife is my sister-in-law. Well, unless she’s my sister, obviously.
I don’t follow why some of you think the sibling-in-law terminology wouldn’t apply to a spouse’s sibling’s spouse, when it’s obviously not a specific term to start with. As far as I can find definitions, it means “someone you’re related to by marriage”, which would definitely include this relationship.
I vote with Anaamika. We need to go mug some other language for more specific English vocabulary. We could still keep the current words for those times when you want to be more general.
Lovely! I’ve been wanting a word for that. Once or twice I’ve toyed with the term cross-laws, but I like the feeling of “with” better.
As to the general relatives of my in-laws thing, sometimes I use the term out-laws. People humor me. Sometimes to the point of patting me on the head.