I think the fourth ranked definition is most accurate, though not as humorous. It’s been my experience seeing people use that phrase in the past, it’s because they want to be non-committal or even evasive, but need to feign current lack of knowledge/resources as an excuse.
OMG. I read the definition.... “sniffs their fingers after going to the bathroom” to see if they need to wash their hands.”
I wash my hands every time. And it’s the first thing I do when I come home.
Could be why I haven’t had a cold in years.
“https://www.urbandictionary.com/define.php?term=Circle%20back“
Went there. Jack sh*t is needed to define “circle back”? And below that they use f*ck and sh*t in the definition of another word.
Maybe that vernacular is where “urban” people feel at home.