A muffy is a sneak attack sexual maneuver. While you're going down on a girl you breath in deep and blow all the air you can muster up into her vagina. Then firmly place your hands on her stomach and press down. The desired effect is a whoopee cushion style queef.
Warning : it is strongly recommended you pull your face away before pressing down.

Can also be spelt "muffy." It's an Australian slang term.
See Bean-o's definition of "muffy." Basically, it's what you'd call "going down" on a woman.

Another word for a mouse

a fluffy puppy whose name is muffy

a girl from clonard that is a slut she is from australia, victoria, geelong

Muffy puffs-a group of hot chicks playing trivia with swollen vaginas at a local pub

n. A generic term that describes any bland, vapid female, like a flight attendant or sorority girl. Her significant other is named "Johnny Package."