| Term | Definition |
| facetious | Witty; humorous |
| facile | Easily accomplished; lacking sincerity or depth; done without great effort |
| fallacious | False; tending to deceive or mislead |
| febrile | Feverish; distinguished by intense emotions or activity |
| feckless | Ineffective; worthless |
| feign | To pretend; mislead; give a false impression of |
| feral | Pertaining to a wild creature; not domesticated |
| fictive | Fictional; fantastical; pertaining to imaginative creation |
| filibuster | To use evasive, obstructional tactics, esp. prolonged speech, in order to delay |
| fitful | Alternately ceasing, lacking steadiness; marked by irregular bursts of activity |
| flippant | Marked by disrespectful lightheartedness or casualness |
| flout | To scorn; to dismiss with contempt |
| fodder | Readily and abundantly available and of little value; raw material |
| forego | To precede; be ahead of |
| forgo | To do without; to refrain from |
| formidable | Fearsome; causing worry; inspiring awe and wonder |
| fortitude | Mental or emotional strength that allows one to overcome difficulties |
| fortuitous | By fortunate chance |
| frenetic | Frantic; frenzied |
| fulsome | Abundant; flattering in an insincere manner |
| furlough | A leave of absence or break; usually granted to a soldier or prisoner |
| furtive | Sly; with hidden motives |