1. To waste time idly, languidly, or aimlessly (in some place); to loiter or loaf around (some place). She's always been an introspective child, preferring to just moon about and contemplate the world rather than playing with other kids. Quit mooning around the house like that—go play outside or something!

2. To desire, yearn for, or grieve over someone or something so intensely that one becomes depressed or melancholy. You can't just sit here mooning about your ex-boyfriend. It's over—you need to get out there and live your life as a single guy! She's been mooning about traveling to Japan since she was in high school.