The title pretty much says it all – I had some prime rib tonight, and realized I’d never heard exactly how it’s classified by meat-type people. Anyone?
ps: prime rib is good.
Its not a steak in that it’s cooked like a roast and then sliced.
Is a roast a steak?
Depends on how you cook it and how it is sliced before cooking.
Start off with a standing rib roast “Prime Rib” (even if the meat isn’t prime grade)
Leave the damn thing whole and cook in an oven the slice = roast
Slice into steaks before cooking and then cook (not in the oven) = rib eye steak.
Confused? 
Don’t even ask which part of the pig is the pork butt.
It’s the shoulder.
Go figure.
Well, ribeye and prime rib are the same cut of meat. The only difference is how you cook them, as Rick pointed out. A ribeye is certainly a steak, so the matter would then depend on whether the cut of meat or the cooking method determines “steakness”. Personally, I would say that the cooking method makes the steak, rather than the cut, since you can grill a roasting cut (such as London broil) and you’d call the result a steak. For what it’s worth, Texas Steakhouse appears to agree with me, since our menu lists Prime Rib under a different heading from the rest of the steaks.
IANAOMP (Official Meat Person). YMMV.
I definitely agree with the above. A steak is a relatively thin (up to 2 inch or so) cut of beef which is cooked quickly under a hot direct source of heat. A roast is cooked for a longer time under a more moderate heat (350 degrees F or so.) A prime rib is definitely a roast and not a steak,