| Term | Definition |
| fiasco | a complete failure |
| fickle | likely to change for no apparent reason; inconstant |
| filch | To steal slyly, especially small things |
| finesse | a) skill, delicacy, or subtlety in doing something or handling a situation b) to accomplish by subtle or skillful maneuvering. |
| flagrant | extremely and deliberately conspicuous; glaring |
| flaunt | To show off in a conspicuous or offensive way. |
| flout | To treat openly with scorn or contempt. |
| fluctuate | To change continually from one position to another |
| foible | A minor, often amusing, fault or weakness in character. |
| forestall | To secure an advantage or prevent a loss by previous action |
| formidable | a) arousing fear or admiration because of the unusual size or superiority of the thing involved b) difficult to do because of the size of the job involved |
| fortuitous | Occurring by chance or accident. |
| frugal | a) thrifty or economical in the use of money. b) involving little expense; meager |
| fulsome | Excessive and, for that reason, offensive to good taste and obviously insincere. |
| futile | Incapable of producing the desired result; unsuccessful or ineffective. |