If you see this in a recipe, it stands for Milk Fat, the fatty portion of milk. Milk and cream are commonly sold based on the amount of milkfat they contain.
an abbreviation used for "multifactorial" to describe when there are many issues/problems/things in your life that are contributing to your current emotional status.
Friend 1: "Hey! How are you?"
Friend 2: "Not too good, actually".
Friend 1: "What's the problem?"
Friend 2: "It's MF".
Friend 1: "Oh, I'm sorry!"