gimf is used to describe an attitude. In the area of popular music (rock, pop etc) musicians who are being "gimf" are writing and recording music with half an eye on quantity as well as quality - it means having an open mind about the creation of the music. For example, a band may toil for months producing a song for a CD single, and as extra tracks, may well include songs that were recorded in a hurry and deemed not polished enough, these tracks would be "gimf".
Two musicians are recording together. One says "Are you sure this is going to work, it sounds wierd", the other one replies "Don't worry, it's gimf!"