| flasque | weak |
| Flat-Out | FlatOut |
| Flatey | Flatey in Breiðafjörður |
| Flateyjarbók | Flateyjarbók |
| Flatheads | Confederated Salish and Kootenai Tribes of the Flathead Nation |
| Flatiron Building | Flatiron Building |
| Flattement | Oscillation |
| flatter | butter up |
| Flatter de la main | Stroke |
| flatterie | adulation |
| flatteries | sweet talk |
| flatteur | congratulatory |
| flatteuse | flatterer |
| flatté | flattered |
| flatulence | flatulence |
