The term "hyena" in the context of a porn video tag generally refers to a specific sexual position or act. In this case, the term itself does not have any specific meaning related to hyenas as animals but is used as a metaphor for describing a particular act.
In BDSM and kink communities, "hyena" can represent a type of bondage where one person's limbs are bound together so that their legs are forced to be spread wide apart, making it difficult for them to close their legs. This position is often used during play or sexual activities as a way to increase vulnerability and expose the bottom partner more fully to the top partner.