(question answered) what's a hemi?

Many readers mobilized to help answer my recent query about what a hemi was. Thanks to all!

A reader from Daktweek, NY, replies:

A google search for "what's a hemi" turned up the following definitions:

a muscle dak.... i love the sounds of that.. work in progress.. i will have
one! there is a guy out west that took a dak and put a cummins 24 twin turbo in
and tweeked it out to 700hp capability. beat the land speed record for that
class vehicle at 220mph roughly.... he was holding the steering wheel with
one hand!!

And, yet more enlightening:

The 727 will work just fine You dont have to worry about it blowing up, if
you prepare it properly. USE A BOLT IN SPRAG! But the glide will put you
about two tenths quicker, but shifting just once during a pass is like
kissing your sister. YAWN!

"Hemi" thus appears to be the password for entering the club of
dak-tweekers, sprag-bolters, sister-kissers, and, presumably,
football-through-tire-throwers.

A backstage-pass-premium-subscriber from Tashkent, OH, e-mails:

Hemi: A Hemi engine has a hemispherical shaped cylinder-head combustion
chamber, like a ball cut in half.

i got this definition from this website:
http://www.nhra.com/basics/glossary.html

as far as i'm concerned, this definition is more useful for me in
situations where someone asks me what a "hemi" is than in situations where
i want to know what a "hemi" is...

A reader from Eighteenth Brumaire, CT, writes:

I think the "Hemi" is when some part of the engine (maybe a shiny air filter) sticks out of the hood, usually people suped up their 70s era dodge muscle-cars (dodge challenger, Dukes of Hazzard) in such a way

as a sociologist i see it (hemi-inspired engine designs) as a way for the working class to feel powerful on the road, with a fast car that's louder than a BMW or Mercedes or a monster truck that you can (theoretically) run over the rich white-collar guy in the foreign-made car with.

A reader from Cedar Rapids, IA (and you know who you are) sent an entry that seemed to be taken from some source of unknown provenance, that included a picture I couldn't upload and artvertisements for Chrysler, some company I'd never heard of called Mopar, and an odd, unnamed enterprise touting this odd fowl dish called a "Goosekey" that is made by taking different hemispheres from a goose and turkey and gluing them together with food-grade adhesive.*

* Seriously, the Goosekey exists and is what I describe, and the reader from Cedar Rapids could tell you all about it in shockingly graphic detail. I will confess to not seeing its relevance to the hemi question.