This porn video tag, "3d-girl-fucked-by-horse," describes a scene where a female character, presumably animated or created using 3D graphics, is engaged in sexual activity with a horse. The term "3D" indicates that the visuals in this porn video are likely computer-generated and use three-dimensional models for both the girl and the horse. In the context of this tag, "fucked by horse" refers to the act of animal intercourse, which is a fetish involving sexual contact between humans and animals. This type of content often appeals to those with a particular interest in bestiality or non-human characters in adult situations.