This porn video tag refers to a specific type of adult content featuring a "milf" - which stands for "Mother I'd Like To Fuck". It suggests that the woman involved is an older, sexually experienced woman who is being aggressively and intensely penetrated by one or more men. In this case, the term "hard" emphasizes the rough and intense nature of the sexual activity. This type of content is often appealing to those with a preference for mature women or those interested in more dominating or rough encounters.