'pi55ing off ' is different to 'getting pi55ed', and 'pi55ing off/pi55ed' has different meanings depending upon the context.
E.g.
I'm pi55ing off out a here -> I'm gone, see ya.
I'm pi55ing off the missus -> I'm making her angry.
The missus is pi55ed at me -> yep, she's really angry at me now.
The missus and I are getting pi55ed -> we're on a bender, probably not gunna get my leg over if she goes too hard.