A song by 3OH!3. There is really no know definition but most people assume it has some relation to the Columbine shootings, because the chorus goes N-E-A-T-F-R-E-"A-K-47". Still all in all a good song.
Random Girl Skipping Down the Street: "N-E-A-T-F-R-E-A-K-47 baby!"
Random Other Girl: "Woah did you know that song is about the Columbine shootings!!"
Random Girl Skipping Down the Street: "Ok then!" continues singing neatfreak 47