The experience of feeling sure that one has already heard a "new" Foo Fighters song, stemming from the bland, generic, and repetitive nature of Dave Grohl's songwriting.
Guy #1: Hey, what do you think of this new Foo Fighters single?
Guy #2: New single? No, you're confused, that song came out in the 90s. And then again in '05 and again in '09. Dave Grohl loves rereleases.
Guy #1: You've got Déjà Foo, buddy.
The peculiar feeling that you get when programming, leading you to believe that you've written the particular code or program that you are currently working on, before.
After refactoring his game engine for the fourth time, Vincent was struck with a distinct, uncomfortable sense of déjà foo.