If I were to gather together fifty new Le Cordon Bleu culinary students and ask them how they feel about the French preparations called pates and terrines, I'm fairly certain that many wouldn't know what I was talking about, and the majority of those who did would claim to dislike those types of dishes for one reason or another. If I was to then ask that same group of students about their relationship with meatloaf, I can almost guarantee that most of them would recall fond memories and a definite affinity for that American comfort food classic. What most foodie newbies don't realize is that, for all practical purposes, the ground meat mixtures that go into producing a delicious pate or terrine are almost exactly the same thing that an American cook ends up calling a "meatloaf".
When you combine ground meat (beef, pork, lamb, venison, rabbit, duck, turkey, etc.) with something starchy (breadcrumbs, bread cubes, oatmeal, cooked rice, crushed crackers, etc.), and then add eggs, salt, pepper, and other spices, herbs, or flavorings, you have just prepared the foundation for what could be become a meatloaf or a pate en terrine (the word terrine originally referred to the earthenware vessel in which the ground meat mixture was baked), depending on how you choose to serve it. The ground meat mixture itself is typically called a "farce" or "forcemeat"...basically a meat based stuffing, very similar to bulk sausage.
See, for the most part, the biggest difference between a terrine and a meatloaf is that a slice of a terrine is often served room temperature or slightly chilled, while a slice of meatloaf is usually served hot. But these rules are certainly not absolute, as we have all probably had a darn good meatloaf sandwich at some point in our lives that utilized slices of a leftover meatloaf just out of the fridge. And, conversely, the French will oftentimes serve a slice of a terrine or a pate en croute (a terrine baked in a bread dough shell) warm. Another difference that worth pointing out is that Americans tend to think of meatloaf as the meat component is the main course, while the French treat a slice of pate or terrine as an appetizer. Other than those minor discrepancies, we're talking about the same thing.
I use this argument on my students sometimes just to get them to open their minds and try a slice of a terrine. Once they've tried that first delicious bite and made the connection to something familiar, safe, and good, there's no looking back.