To move slowly around or stand in a public space without an obvious reason. (Cambridge Dictionary)
To go slowly, stopping often. (Cambridge Dictionary)
If you loiter somewhere, you remain there or walk up and down without any real purpose. (Collins Dictionary)
To delay an activity with idle stops and pauses: Dawdle. (Merriam – Webster)
To remain in an area for no obvious reason. (Merriam – Webster)
To lag behind. (Merriam – Webster)
Stand or wait around without apparent purpose. (Oxford Dictionaries)
Walk slowly and with no apparent purpose; dawdle. (Oxford Dictionaries)
Loitering with Intent – Detecting Suspicious Behaviour using Video Analytics.
For Your Own Sake, Loitering and Loafing: Know The Difference.