The term "giantess-city" refers to a specific subgenre within the realm of adult content, specifically related to Giantess fetishism. This tag implies that the video features a setting or scenario in which a person (or people) becomes a giantess - an incredibly large woman, sometimes many times larger than buildings and other urban structures.
In these scenarios, the giantess may interact with a city and its inhabitants in various ways, such as crushing or towering over vehicles, people, and objects. The focus of this subgenre is often on the extreme size difference between the giantess and her surroundings, leading to fantasies of power and control.
In summary, "giantess-city" indicates a porn video with a setting involving a giant woman interacting with or within an urban environment. This type of content is intended for adult audiences who are interested in this specific fetish.