The term "gay-cum-eating" refers to a specific subgenre or category within gay adult films and content. In this context, "gay" refers to the sexual orientation of the participants involved in the video, which is primarily focused on interactions between men.
The phrase "cum-eating" specifically describes the act of one person consuming another's ejaculate or "cum". This could be either through actively licking it up, swallowing it, or any other form of consumption. It also implies that there is a focus on this act within the video.
In summary, "gay-cum-eating" would indicate an adult film where the content focuses on explicit interactions between men and includes the act of consuming ejaculate as part of the sexual activity.