The Actual Definition Of Steak
According to the dictionary (Merriam-Webster, to be a bit more specific), a steak is a chunk of meat sliced from a cow's carcass. The "fleshy part," to be specific, since who wants to chew on a chunk of cartilage or gnaw on a bare bone? That, more or less, is the gist of the first definition given, one that for the most part seems to match up with what most of us have in mind when we word-associate.
There are a number of other, alternate definitions, however, that do cover non-beef applications of the word. A pork steak, for example, is a hunk of pig cut in a similar style to a beef steak, whereas a ham steak is simply a thick slice of ham. Fish steaks, too, can be a thing (here's a recipe for tuna ones) as can cauliflower steaks suitable for vegans (try cooking these in the air fryer). Still, alt-steaks aside, the fact remains that in most people's minds, a "true" steak is the kind that comes from a cow. A steakhouse, after all, is a restaurant that specializes in beef, not in steaks of any other variety.
The courts have decided that ground beef can be steak, as well
Going back to that Merriam-Webster dictionary definition, though, there is no need to assume that a beef steak necessarily consists of an intact piece of meat. A secondary definition of the word is applied to ground beef, particularly when it is formed into a shape that somewhat resembles the more familiar form of steak. Swiss and Salisbury steaks can fit this secondary definition and so, too, can a hamburger, as was decided in a court of law in 2020.
Several years ago Dunkin' added a few new items to the menu, to wit, an Angus Steak and Egg Breakfast Sandwich and an Angus Steak and Egg Wake-Up Wrap. One litigious-minded and linguistically-persnickety patron smelled a lawsuit in this "deceptive" advertising, but ultimately their attempt was unsuccessful. Courts determined that no deception was intended on Dunkin's part and that the chain could keep on using the term "Angus steak" to describe the breakfast burgers despite the meat's not being "intact." Steak and Shake, no doubt, was relieved by the ruling, as this chain has been around for nearly 100 years selling "steakburgers" that are also made from ground beef instead of slabs of sirloin.