In reference to when a baby is born, the outer part of the vagina flaps in and out for about a second or two. This gives the appearance of saloon doors opening and closing like in old western movies when a cowboy walks into the place.
Did you see that that chick give birth?! That baby cameflying out of those saloon doors.
The professor and Roberto were so scared of their sexuality that while on the road in the cover of night they took the chance to act on their saloon door syndrome.
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.