2.) A way to tell a person that someone they are talking about is in earshot.
3.) Telling a person their actions are completely and utterly embarrassing to you (can also be used with a kick to the shin, an evil glare, or a jab of an elbow to the ribs).
J: So mom I saw this funny thing on the internet, It's from A play called Avenue Q. My fav song is "The internet is for porn."
Mom: (Almost swallows her tongue and chokes)
Me: "Snakes On A Plane J, Snakes On A Plane!"
J: (doesn't realize the volume of speaking which is usually loudly) "Man that chick over there is so fat, I can't believe someone would get that fat!"
Me: "Snakes On A Plane!" "You said that too loud we gotta go before we get crushed." "Run!"