To "man up", or start acting like man. Refers to the act of reversing the tucking (thus untucking) one's junk (i.e. penis) between one's thighs.
Kenny: I like this girl, but I am not sure sure she'll go out with me. What if she says no?
Goldie: Dude, untuck your junk from between your legs already, and ask her out!
Kenny: Okay. Goldie, will you go out with me?
Goldie: I don't appreciate this, Kenny.
Infamous, now viral, phrase uttered by John Tyner of Oceanside after refusing to be subjected to an airport body scanner and subsequent thorough pat down.
Can also be used in any social setting where you just want people to stop bothering you with uninteresting things.