A phrase to discribe an extreame passion or emotion. Usually positive, but can be negitve if the case is that bad.
Often likend a volcano that is about to errupt.
"I am so fired up for tonights game"
" Hey we are going to the bar to rope some cattle and knock down some soldiers... Fire Up"!
" I just killed a monster buck with excellent brow tines and G3's, pure Muzzy power... FIRE UP"
" I am sick of my taxes going to fund stupid programs... I am fired up"