An octopus-like creature with four tentacles that lives in Snifoo world. You can be a snifoo by putting your fingers to your mouth in a spider-like fashion and wiggling them. This tentacle mouth part is called a "sneef". They like to make sounds like this: Drooo droo droo dooo. They talk like snifoos. They say "Me" a lot. Say "yous" instead of you. They love to play tetherball.
the pronouciation of the acronym STFU which means shut the fuck up. Stiffoo is just a better way of trying to say the letters, or more pg way of saying the full meaning. It also seems to lose some of its aggresion with the abbrivation.
person 1: so i was like 'blah blah blah' after she was all 'yadda yadda yadda'
person 2: god, stiffoo!
person A: stiffoo noob!
person B: why dont you just swear like a normal person?