rack your brains | rack you brain
Meaning: If you rack your brains, or rack you brain, you try hard to remember something or think of a solution to a problem or a puzzle.
- I'm racking my brains, but I just can't think of his name.
- Shelley's writing this song about being out of work and she's racking her brain trying to come up with a good rhyme for "unemployed".
Sometimes I have to rack my brains if I want to