Hummer-head, in its most accurate usage, is recieving or giving oral sex while inside of the Hummer brand of SUV's. It's implied that the person giving hummer-head is the passenger and the person recieving is the driver, and it is also implied that hummer-head is achieved while the vehicle is in motion, but it can also happen when the vehicle is stationary, obviously. Although hummer-head has an obvious denotation, its connotation is more important. Hummer-head is more of a display of power and egotism than it is a sexual act. Hummer-head is generally induced by those bad-ass individuals who are ridiculously buff, have a tattoo of the nautical star somewhere on their person, and are generally either deliberatly bald or participate in the age-old douchebag tradition of "fo-hawk"ing it up. These men "got to have it now" and convince their "woman" to "come on, baby" and give it up. A favorite tradition of these D-bags is to scream "Ohh yeahhh!!!" during the point of climax and usually follow by the demeaning practice of fucking the woman's mouth as if it were a vagina. Hummer-head is not restricted to actual Hummer brand SUV's, the "Hummer" part of the term is just a symbolic reference to the type of vehicle the head is given in and the meaning behind that head. Hummer-head can be given in any sort of large truck or flashy SUV where the goal is more of feeling like a badass than actually getting head, although the sexual gratification is certainly "pretty fuckin sweet, babe". Furthermore, Hummer-head can also be a verb, as in the man "hummer-headed" that bitch like no tomorrow. This may present a little pronoun confusion, as the verb hummer-headed may suggest that the person using this verb in a posessive state is doing the actual head giving. However, this is not true. When the recipient of hummer-head uses the verb hummer-headed, he means to display superiority as a male and slightly demean the woman who is giving the head, as to show her who's really "the man". Thus, when a man hummer-heads a woman or when he has already hummer-headed her, he has done so with the generally concious goal of asserting himself as the dominant figure of not only the relationship, but humanity in general, keeping in mind that the person who recieves hummer-head or hummer-heads a girl is a magnificent prick.
"Yeah man, I got totally fucking ripped at the gym today. I think I'm gunna motor on down to the store and get a protein shake and probably get hummer-head from that one bitch on the way."
"Dude, that's a fuckin sick nautical star tatto, congrats on the hummer-head btw, I saw the video on your cell phone."
"Fuck man, I hummer-headed that bitch."
"Yeah, I heard after he bought that shitty 1970's Ford pickup truck, raised its suspension by 4 feet, attatched spotlights on the top and a gun-rack in the back window, he hummer-headed his bitch hardcore."