There's a lot of different definitions of it, but I get the impression it's basically a guy who's really nice to girls to get them to lay him. The excerpt given at the top of the Google search results says it's a misogynistic term, but I don't see it that way. In today's "woke" culture anyone will say something is misogynistic with a hair trigger just to gain PC brownie points.

I think the term just highlights how unequal/gynocentric the dating world is. Girls/pussy are in such high demand that guys will go all out for them while the girl doesn't have to bring anything to the table. It's not really fair.. not that anything about life has ever been fair. Girls say they have it harder than guys, but things like this make it seem like they have a huge advantage. I hate being a guy and wanting a million beautiful, delicious girls that I can't have. It's all I really want. So it's like being a dog and having treats waved in your face all day and never being allowed any of them. And I'd hate being a simp because it's humiliating rolling out the red carpet for someone who does nothing in return but allow you access to her body. It's kind of a toxic dynamic. I don't think it's healthy for the girl either to have someone wrapped around her finger like that. And, like (I think it was?) Pawesome, I'm kind of skeptical that the approach even really works.

(BTW, regarding girls having a huge advantage, yes, I know girls have challenges that I, being a guy, know nothing of.. I just want girls to see guys' side of the equation here.)