prowl 
(proul)
(proul)v. prowled, prowl·ing, prowls
v.tr.
To roam through stealthily, as in search of prey or plunder: prowled the alleys of the city after dark.
v.intr.
To rove furtively or with predatory intent: cats prowling through the neighborhood.
n.
Idiom: The act or an instance of prowling.
on the prowl
Actively looking for something: salespeople on the prowl for better jobs.
[Middle English prollen, to move about.]
prowler n.