To have big muscles or to be all "jacked up" but with all natural training, and without the aid of performance enhancing drugs and steroids.
Person 1: "Look at that dude! He's huge! He must be on steroids!"

Person 2: " No man, he's an all natural beast! He's legally pumped!"
by nicholasbrunello January 21, 2010
Get the legally pumped mug.