It's mainly a word used when your about to go into a club and be lit or live and have fun
Or you can use it to say to your friends that your
Going to pipe up a girl
Or you can use it like this
Boy 1 : what you doing tonight let's go out !
Boy 2 : I would but I'm chilling with this girl tonight you know Ima be pipin it up!
Originally a naval expression. It means stop talking and be quiet. The Pipe Down was the last signal from the Bosun's pipe each day which meant "lights out" and "silence".