Lust is a strong sexual desire or passion. In the context of this porn video tag, it refers to an intense feeling of sexual attraction that drives the actions of the individuals in the video. The "man standing" part simply describes the position or situation of a male participant, implying that he might be displaying his body and available for interaction. So overall, this tag could refer to a scene where a man is standing, showcasing his body, while experiencing strong feelings of lust or sexual desire.