SHL: Reminds me in English of calling a urinal a “pisser”
I would rather think that a pisser is the user of pissoir.
...still having doubts what would be the pissee then 
Alharacas taught us a new word, idiolectally (even my spell checker is flagging that in red)....it reminds me of a medical term, like idiopathic or something.
And, MartinSR and I are voting to upgrade Pissoir in German and start using it more. Maybe it will come back into style. It’s got that elegant French sound to it, that „oir“ ending. Yeah, I really saw one along the roadside, somewhere up north (never saw these south of Hannover I believe), off the Autobahn. Just a big sign „PISSOIR“ and I was glad to find it too (too much coffee that day I’m sure). But, those really were standing-style only places- sorry ladies, just keep on driving. Just a guy‘s place. Lots of truck drivers.
MartinSR does have a good point. It we were to adopt this in English, we‘d have to call it a „pissee“ because the user would be the „pisser.“ That has sort of a legal ring to it. Like trustor/trustee. Makes sense.
