1. used to describe one who is acting in a nerdy and/or uncool manner ie: acting not normal or weird
2. also can be used as an adjective to describe something that is not quite right
3. can also be interpreted as the hair around a womans vagina

This definition of muffy originated back in 1997 when I was in high school. An un-popular girl at my school had a head of hair so poofy and frizzy it resembled a big muff on her head, so we started calling her muffy. The word slowly became an adjective, and started to replace other words in our vocabulary (ie: your hair is muffed instead of your hair is messed up, and what the muff, instead of what the fuck)

When you eat dirt for the first time and leave your family to build a shack in the woods