A description of the current time which is valid when the speaker/sender is in a timezone where it is morning, and the hearer/recipient is in a timezone where it is the afternoon.
A combination of morning, afternoon and evening. A general all-purpose time-unlimited period of the day. Usually used when you've got up so late that you can't really say "good morning" any more, and even "good afternoon" is pushing it.
- My god, you've only just got up?!
- *yawning* Good mornernoonening!
It's the contraction of morning and afternoon. It's mostly used at work when you start your day, but people on a different timezone are already in their afternoon.