A work day that begins on Sunday, and may last through the end of Monday. Typically, this is used to indicate a shortened weekend because of work-related duties. 2. Getting a head start on the week by starting work on Sunday night.
1. I can't go camping, my boss called me in for a Sunmunday. 2. Don't talk to me, don't look at me, just let me go home. I just worked a 36-hour Sunmunday.