Pork Butt Defined (condensed from numerous sources, and supplemented with my experience)
Despite the name, pork butt does not come from the rear end of the hog.
The "butt" is actually the front shoulder.
A pork shoulder may average from 10-20 pounds and consists of two parts: the butt and the picnic. Both make excellent pulled pork. A whole pork butt is a rectangular roast weighing 6-12 pounds and may contain a portion of the shoulder blade bone (or not... hence "boneless butt"). Keep in mind that one thing that the bone does not do so well is transmit heat to the interior of the roast.
The picnic may average 6-9 pounds; and is a portion of the foreleg and is usually sold with some skin attached. This piece tends to have more "waste" as you will end up removing that skin, etc.
Other Names For Pork Butt:
Boston shoulder roast
Shoulder blade roast
Fun with Pun's (we all have thought of these)
You want to find a nice (piece of) butt.
Make sure to tell your butcher: “I want a butt. Make it a big butt, too, please.”
It could be a fat butt.
When driving home with the butt, you are hauling butt.
When on the smoker, it becomes a hot (piece of ) butt.
If your rub contains a large amount of sugar, it could be a sweet piece of butt.
If you use kitchen twine to tie the butt... (OK, I won't go there).
The fun goes on and on.
Both the Butt and the picnic portions contain a lot of fat and connective tissue. When you cook them low and slow, magic happens and the result is awesome Q.
Choosing A Pork Butt
All pork is inspected for wholesomeness by the USDA, but is not always "graded". I have read in places that the USDA claims this is because pork is "produced from young animals that have been bred and fed to produce more uniformly tender meat." Whatever. No two butts are alike.
When I look for Pork Butts, I look for untrimmed butts weighing 8-10 pounds each. Choose pork butt with a uniform, white fat cap and a good amount of fat marbling within the meat itself. The meat should be red-pink in color with a coarse grain. Cryovac units may look purple, but will "red up" when exposed to open air for a few minutes.
The way I prep a butt for smoking is to remove it from the packaging, pat it dry with paper towels. I then trim the fat cap off. Why? Smoke and rub won't penetrate the external fat and you waste precious "bark". The butt has enough fat internally to baste itself from within without the cap on. You'll want a large, sharp knife to trim a butt. Trim it off however you feel is best, just dont trim off too much lean meat. Next, trim any other large areas of external fat and veins, blod spots, lymph nodes, etc. that you find. Trim them down to the lean meat. If you find pockets of fat, trim out whatever seems reasonable. However there is such a thing as too much trimming, so don't trim it all, just the major stuff and anything that isn't something you wouldn't want to find on your plate.