Question: I have come across it in the six episode of the first season of *Rick and Morty*. Here is the context:

> 
> Jerry: Ahhh, well, (gets another jar of sauce out of the cupboard) I remember feeling that way about a young lady named your mom, and that's not an **urban diss**, your mom was my Jessica. I remember the first time I saw her, I thought...
> 
> 
>

Answer: 
*Urban diss* is not a common phrase. It's made up of these two parts:

> 
> **diss** noun
> 
> 
> *slang*  
> 
> : an insulting expression of disrespect or criticism  
> // … a much loved and much hated album; earning some equally passionate critical raves and *disses*.  
> — Brett Milano
> 
> 
> 

<https://www.merriam-webster.com/dictionary/diss>

> 
> **urban**
> 
> 
> *adjective*  
> 
> ...  
> 
> **4** of or relating to the experience, lifestyle, or culture of African Americans living in economically depressed inner-city neighborhoods:  
>  *Their first album had a hard, urban vibe.*
> 
> 
> 

<https://www.dictionary.com/browse/urban>

Together, this would mean: *...and that [comment about your mother] is not an insult of a type that's associated with African American culture...*

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Why does Jerry say this?

1. He intends to clarify that when he said, "I remember feeling that way about a young lady *named your mom*", he was not making a ["yo momma" joke](https://en.wikipedia.org/wiki/Maternal_insult). He wants to say that he was speaking literally.
2. This character is meant to seem painfully unhip.

* This use of *urban* is marked. Popular perception seems to hold that only people who use *urban* as a sort of euphemism for *Black* are out-of-touch. It sounds like something a politician, or a marketing executive might say.
* *Diss*, especially as a noun, is similarly marked. This word came to mainstream attention sometime in the 90s. You might have been cool if you used *diss* in 1998. In 2013 (when this episode first aired), and if you were a parent, using this word would make you look like you were trying hard to seem cool, but were very behind the times.
Urban diss = inner-city put-down or insult. "Your mom" (yo' momma) is a type of joke. Example: Yo' momma's so fat that she has her own zip code!