look up any word, like ratchet:
 
1.
Male (or female) body builder whose only concern in life is bigger muscles. Usually implies little-no brain activity.
John is a complete muscle head, nice to look at but nothing upstairs.
by Xavier2 January 15, 2007
 
2.
A selfish, narcisstic, egotistical person in the gym or fitness center. One who is a bodybuilder (see also body builders) or aspiring strength maniac who usually looks at others with disdain unless they need them for a spot. They almost never put their weights away when they're done with their exercise -- sometimes leaving a pile of 45's (45-pound plates) next to the machine or leaving a heavy load of plates remaining on the machine. They usually either wear shredded, revealing clothes or hide their bodies (or bacne) under thick, cotton sweatshirts and sweatpants. They also might wear heavy clothes to keep warm and avoid the chills from feeling so lousy while they are in ketoacidosis and dropping body fat before bodybuilding competition. Or, maybe they just prefer old school cotton sweatshirts over newer synthetic fitness attire.

The extreme muscleheads appear to be angry and on the verge of an outburst, possibly a state of roid rage. If you are on a machine that they want to use, they are likely to just stand nearby and stare at you while you are exercising, instead of asking you how many sets you have remaining or whether they can 'work in.' The extremists also tend to drop weights or toss dumbbells after their last repetition.

Think ... the gym version of a road hog in traffic.
Dude, YOU ask that musclehead to put his plates away!
by Mark Bostrom January 13, 2007
 
3.
An automotive enthusiast who believes in the philosophy that the bigger a car's engine, the better it is. Used in a perjorative fashion.
If you take 2 cars, one with a V-6 and one with a V-8, the stereotypical musclehead will always believe the car with the V-8 is better, even though the car with the V-6 may actually be faster for other reasons (lighter weight, higher displacement-to-horsepower ratio, turbos, superchargers, etc.), have better handling and response, etc.
by D.L. Crosse February 01, 2007
 
4.
1. import hater
2. a person that thinks any other car then a USDM car is crap.
3. A person that does not know any thing about cars just that there car can beat any car out there because its an american car.
4. The usual american car driver that claims he/she beat every car out there even if no body has ever seen these cars he/she has beating or even seen this person race once.
5. The american version of a ricer.
I hate it musclehead puts a flowmaster muffler tip on a car and claims it adds 50hp+ but makes fun of a ricer that slaps on a coffe can tip and claims that same crap. I love it when they add an aggressive cam and start the car up only to hear the death rattle of valves smacking the pistons. "Slap a cam in there and slam on a flowmaster tip and that car can beat any thing"
he/she buys a base model mustang and claims he can beat a porsche 911 because the 911 is a "crappy import"

musclehead "I beat a crappy ferrari with my (insert typical american mid sports car here), to bad you did not see me"
by i hate musleheads September 02, 2005
 
5.
A muscle head is someone who spends all their energy with their head in a book.
Muscle heads are the guys who you do not like in high school who end up making six figures after you graduate. Brain always wins over Brawn! You go muscleheads!
The musclehead stayed home from the party while we had fun.
by Bonnie Ryan August 17, 2006