Question: Is there a word that describes or denotes a type of conversation in which two speakers speak two different languages. In our country, Pakistan, there are approximately 75 languages, from which Urdu, Punjabi and Sindhi are common, excluding English. So today I found two women speaking two different languages. For example: Speaker 1 has Urdu as their mother tongue. Speaker 2 has Sindhi as their mother tongue. Speaker 1 and 2 spoke their own mother tongue, which are different (Urdu and Sindhi) but both can understand each other's language. I thought that this is known as "intermingling conversation," or a "code switching." In my opinion, we can't use such words because code-switching refers "shifting completely to the other language for a word, a phrase or sentence, and then revert back to the base language." Example sentences: They were in a bus and had [adjective] conversation. They were in a bus and had [noun or noun-phrase for such conversation]. I agree that the question (which is suspected as a duplicate one to this question) is really a duplicate, but its single answer still doesn't satisfy all. In that question, the phrase "bilingual dialogue" was suggested, which I (and others may) think that this refers to the code switching as well, which I don't want here. Some words confuse the readers which sense do they mean. I would also love to quote the comment of @Lambie regarding the term "bilingual" over here: "Bilingual refers to one person. Not two people each of whom has a passive knowledge of the other's language but do not speak it well enough to use it actively." 
Answer: I am a translator and interpreter and speak four languages (I am quadri-lingual, in fact). There is no specific term for this. And it's certainly not bilingual. If this refers to two people, it just means they at least passively know each other languages but actively only use their own. They each have a passive knowledge of the other's language, otherwise they'd be speaking one or the other. They are passive "speakers" of a language. passive speaker Passive knowledge means you can understand a language or read a language but cannot actively speak it with any confidence. For example, in my case, I speak three Romance languages but do not actively speak Italian. However, my passive knowledge of Italian is very good so I can actually carry on a conversation with an Italian speaker if they can understand English. (In fact, I can carry on a simple conversation but can understand an advanced one passively.) But beware: In the world of translation and interpretation, a passive language has a more technical meaning: it means the language from which a translator or interpreter is working. This is often symbolized as: German>English, English>Chinese. If a person is bilingual (which is not as frequent as one might imagine), this is signified like this: English<>Chinese. Here is a blog post about this issue as regards active and passive vocabulary in language learning, though it applies to monolinguals as well. passive and active vocabulary I often speak English to my husband and he responds in Spanish. We have a conversation in two languages. Bilingual means an individual can speak two languages equally well, though there are different levels of bilingualism. And, if I hear someone say: "We had a bilingual conversation." I would understand that each of the speakers spoke two languages and both switched back and forth between those two languages without causing a break in their conversation due to lack of understanding. As for codes, mixing and switching them is not "inter-lingual". A speaker code switches within her or his own language. Reading over the answers, I had to laugh when thinking about having a conversation with someone where one person uses a different language than the other and they understand each other. Of course, they understand each other, otherwise it would not be a conversation, would it? And, I daresay that mutual intelligibility is an issue that does not involve more than one language necessarily. Who hasn't had a conversation with eggheads in a monolingual situation where there was no "mutual intelligibility" at all? And for the record, the idea that a Spanish speaker can understand a Portuguese speaker is a very specious idea. The fact much in the two languages is very similar does not account for the parts that are completely different. And this can lead to major misunderstandings and comical situations. (I just can't think of an example at the moment, as I write.) The mutual intelligibility factor is true only to a limited extent.
Output: no