Are "weight Gainer" powders called that just because of the amount of calories being so high? Couldnt one just drink a shake like that as a meal replacement instead of in addition to a meal? For example. Muscle milk used with milk is 600+ calories, is that considered a weight gainer when taken in addition to a meal, but a meal replacement if taken alone?

Shakes like that (and Muscle Milk is especially dangerous because it is so darn tasty!) can definitely be used as meal replacement. Muscle Milk is pretty high in fat, so I'd watch out there. It's all about the macros and the calories. The shakes are just a quicker/convenient/and more efficient way to eat the calories you are shooting for. Just don't go overboard with them, but 1-2 per day isn't a big deal.

consuming mm like i do is within my ratios so id be ok. Anyone know a good mrp thats ~500 cals with milk and somewhat tasty, but less fat than mm?