Someone who uses a variety of
underhand tactics to try and get laid because, having serious problems with misogyny, a roaring
inadequacy complex, a deeply warped image of what constitutes being a worthy person, have never developed a healthy way of interacting with the other sex and seem to believe that the only way to get laid is to beat the other person into submission or trick them, they believe that this is somehow a reasonable way to behave.
By and large, so-called PUAs are inexperienced people talking
scarily ignorant shit at each other to try and appear more experienced than they are, or have some degree of success - if it can be called that - which amounts to having sex with a string of women as ill, sociopathic and/or desperate as they are, or ones who are too stupid to realise what a scary manipulative misogynist the person edging ever-closer to them is.
In other words: they have the amount of sex they would otherwise have if they were just perfectly honest about their ends, minus all the people they've scared off by being clearly desperate and/or not very well in the head.