Warboss
ALRIGHT YA MANGY GROTZ! LISTEN UP, CUZ I'Z DA BOSS NOW!
A Warboss is the biggest, baddest, meanest ork in a tribe, and the second-biggest possible type of ork within the species - the biggest being the Warlord. These guys have been through a hell of a lot of fights, and the respect and submission that their tribe shows for their prowess has caused them to reach gargantuan size. While your average ork boy is pretty shooty and/or choppy, the Warboss (or "da boss" to one of da boyz) is the biggest and baddest without a doubt.
A Warboss is what you get when a Nob rises through the ranks of the tribe through either cunning brutality or brutal cunning (or a mixture of both), eventually making a power play against the reigning Warboss and nabbing his spot (and all the shiny gubbinz that come with it.) Sometimes this turns out differently, with the Warboss dying in a genuine scrap with the enemy while his Nobz all fight amongst themselves for the right to take his place.
A Warboss leads from the front, eager to have the chance to add some heads to his pole. Don't think they do this lightly, though - Warbosses are always keen to slap about the Meks of the tribe to make them give them the shiniest bitz. Despite their pretty much single-minded focus on warfare, they often end up gearing up completely differently than one another based on preference and clan. This just as often results in the already ridiculously huge bastards having Mega Armour or something welded to them as it does having a bitchin' bike to chop heads off from at high speeds.
Warlords are the biggest of the big - so big that they can command many tribes under their flag into one big Waaagh! These are the most exceptional individuals of the orkoid race, as one would expect from an ork so big he can boss other Warbosses around.
The Warboss of a Freebooter group is called a Kaptin.