A phrase originating in northern MA which if used literally is to tell someone to tuck their penis into their pants. It is more commonly used to tell someone to cool down or to stop trying to get with a girl who is clearly not interested.
Person One (to a hot girl): "Hey, wanna come over to my place later?"
Person Two: "Yo dude, tuck it in."
#chill#relax#chillax#chill out#lock it up#get your shit together#pull it together#get your head in the game