[Doing something] On and off = Sometimes yes, sometimes no. More off than on = Mostly no. Example: Q1: Do you usually walk to work? A1: On and off (Sometimes) Q2: How often do you walk to work? A2a: More off than on (Not very often) A2b: More on than off (More often) P.S. Think of a light switch: On/Off. The second part is unnecessary and a rarely used slang.

Ok, so for example if you asked me if I still saw my friend Stephanie and I said "off and on" it would mean that I would see Stephanie maybe every day for two months then not at all for 2 months then every day for two months. If I added the statement 'more off than on' it might mean that I only see Stephanie for a couple of days and then I don't see her for 2 months, then I see her for a coffee, then not again for another longer period of time. I hope that makes sense.