Usually asked to your partner(s) in less than legal deeds when you think the cops may be afoot but are not completely sure or don't see them. Can also be used to bring up the suspicion that somebody may be a cop to said friend.
Can also be used as a phrase to alert homies and ask them to look around for police activity in the area.
May have originated from the movie "Wayne's World" when character Wayne Campbell asks Garth if he smells bacon in front of a police officer outside a diner.
Stoner 1: "Do you smell bacon?"
Stoner 2: "Yea man, put that shit out."
*hides joint as cop turns around*