What is Your Mouth Is Open?
1.
Speaking without authority or unclearly.
Usually used amongst friends, can be a merciful out for a person who starts talking and realizes halfway through their speech that they haven't a clue what the point they were trying to make was.
Your stoned friend who keeps endlessly blabbing on and on about the blue dophins of conciousness holding his eyelids open with a toothpick could be quickly shut up by being told "Dude - your mouth is open!"
See
