Air Marshal John

Generic term for someone who looks like a cop, air marshal or any type of law enforcement, but it dressed like a normal person. See: scenes from Bridesmaids, particularly their failed flight to Las Vegas.

Bro, put away the pipe...that guy in the dockers is a total Air Marshal John.
It's fine to drink in public, just look out for Air Marshal John.
Whoa, Air Marshal John alert - that dude in the short-sleeved dress shirt is definitely a cop.