Moon around
Definition 1 of 2
Pro Tip 1/3Daydreaming focus
Used to emphasize someone's lost in fantasy rather than being productive or attentive. 
He's been mooning around thinking about becoming an astronaut again.
Pro Tip 2/3Emotional state
Suggests a person is feeling lovesick or emotionally distracted. 
Ever since their first date, Mia's been mooning around sighing happily.
Pro Tip 3/3Non-literal moon
There's no actual moon; it's a metaphor for being absent-minded or dreamy. 
Alex mooned around during class, barely listening to the teacher.