[Yukihiro Matsumoto <matz / ruby-lang.org>, 2005-05-08 17.13 CEST]
[...]
> I'd like to emphasize the "per-object" attribute of the object.
> Ideally, the term should be "xxxx class" where 
> 
>   * xxxx describe the class is per-object.
>   * xxxx is an adjective, or a noun that can be used like adjective.
>   * we can call methods now we call "singleton methods" as xxxx
>     methods for consistency.

"Particular"?

(In Spanish it fits perfectly, but maybe is a false friend...)