"Sucking-Hard" is a porn video tag referring to a scene or act in which one partner is performing oral sex on the other, with a strong emphasis on intensity and enthusiasm. This suggests that the person giving oral sex is doing so with great effort and passion, often using their hands as well for added stimulation. The "hard" part of this tag implies that both partners are enjoying it and engaging in intense sexual activity. It's meant to suggest an energetic, powerful, and pleasurable experience for everyone involved