basically means that you're friends, but both of you know that there's a possibility of you becoming an item in the future.
julia: we decided on being fwp, so we'll see where it goes from there
Usual indicators are found in the ankles and cheeks in particular
(2) To disprove a suspected prinny or flatspot.
"Oh, nothing really. We hung out for a while, I made sure she was satisfied, and we went to sleep."
"Oh man! You FWPed the shit out of her!!"