Big Choppas are crude, large, 2 handed melee weapons, usually wielded by Ork Warbosses and Nobs.
Formerly called Uge Choppas, these weapons are usually shaped like huge axes with plenty of "spiky bits" giving the weapon a more aggressive look. Their unsubtle design is capable of packing a considerably harder hit than regular Choppas. This power is paid for by having to use both hands to carry and wield the great weight but, to close combat crazed Orks, having a bigger, badder weapon to smash your enemies brains out with is (only a little) better than a gun.