| Term | Definition |
| floe | mass of floating ice |
| florid | ruddy; reddish; flowery |
| flotsam | floating wreckage |
| flounder | struggle and thrash about; proceed clumsily or falter |
| flout | reject; mock; show contempt for |
| fluster | confuse |
| fluted | having vertical parallel grooves |
| foible | weakness; slight fault |
| foist | insert improperly; palm off |
| foment | stir up; instigate |
| fop | dandy |
| foray | raid |
| forbearance | patience |
| forebears | ancestors |
| forestall | prevent by taking action in advance |
| forgo | give up; do without |
| forswear | renounce; abandon |
| foster | rear; encourage |
| founder | fail completely; sink |
| fracas | brawl |
| fractious | unruly |
| fraught | filled (with); causing emotional distress |
| frenetic | frenzied |
| fresco | painting on plaster |
| fret | be annoyed or vexed |
| frieze | ornamental band on a wall |
| frond | fern leaf; palm or banana leaf |
| froward | stubbornly contrary |
| fructify | bear fruit |
| frugality | thrift |
| fulcrum | support on which a lever rests |
| fulminate | denounce thunderously; explode |
| fulsome | disgustingly excessive |
| funereal | solemn |
| furtive | stealthy; sneaky |
| fusillade | simultaneous firing or outburst |
| futile | useless; hopeless; ineffectual |
| gadfly | animal-biting fly; irritating person |