This is quite an old phrase, dating back to WW2 at least. To "get a rocket" is to be scolded or told off, usually by someone in authority; boss, manager, teacher, parent, etc. It may go as far as dismissal.
by New Old School January 3, 2012
Get the get a rocketmug. A term used when the funnist kid in the world, Joeseph White, says when he makes fun of English people in Halo 2.
by Steven Levy December 17, 2004
Get the Get the Rocket Launchermug.