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.
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"
musclehead "I beat a crappy ferrari with my (insert typical american mid sports car here), to bad you did not see me"
The musclehead stayed home from the party while we had fun.