What is considered a meal with regards to Kiddush?

The Shulhan Aruch (O.H. 273:5) writes that Kiddush must be followed by a meal, which in this context must consist of at least a small amount of bread or a Revi’it of wine. Fruit on their own, on the other hand, would not be considered a meal for this purpose. Indeed, the Vilna Gaon  (Maaseh Rav #122) rules stringently and says that one must eat bread after Kiddush.

Nevertheless, the HIDA (Birke Yosef, § 273) writes that food whose blessing is Mezonot would also be valid as a meal. Not only does the HIDA permit Mezonot which have the form of bread and if eaten is sufficient quantities, necessitate the blessing of Hamotzi (such as sweet rolls, danishes, etc.), but even Mezonot which can never be Hamotzi such as noodles or fried items. The HIDA’s rationale is that the after-blessing of Mezonot, that is, Al Hamiya, must be said in the same place as in which one ate, and thus one is considered anchored enough to that spot to be considered as having had a set meal. Thus, one would be able to follow Kiddush with Yerushalmi Kugel or Couscous, for example.

Rice requires the blessing of Mezonot but its after-blessing is Nefashot, and therefore, Rabbi Ovadia Yosef (Yabia Omer , vol. VII, Orah Haim, § 35) rules that rice does not have sufficient permanence to be considered a meal. 

Summary: The custom is that any type of Mezonot, whose after-blessing is Al Hamihya, is considered a valid Seuda for the purposes of Kiddush.