| Term | Definition |
| flit | fly; dart lightly; pass swiftly by |
| floe | mass of floating ice |
| florid | ruddy; reddish; flowery |
| flounder | struggle and thrash about; proceed clumsily or falter |
| flout | reject; mock |
| fluke | unlikely occurrence; stroke of fortune |
| fluster | confuse |
| flux | flowing; series of changes |
| fodder | coarse food for cattle, horse, etc. |
| foil | contrast |
| foil | defeat; frustrate |
| foliage | masses of leaves |
| foment | stir up; instigate |
| foolhardy | rash |
| fop | dandy; man excessively concerned with his clothes |
| forbearance | patience |
| ford | place where a river can be crossed on foot |
| foreboding | premonition of evil |
| forestall | prevent by taking action in advance |
| forgo | give up; do without |
| formidable | inspiring fear or apprehension; difficult; awe-inspiring |
| forsake | desert; abandon; renounce |
| forswear | renounce; abandon |
| fortuitous | accidental; by chance |
| foster | rear; encourage |
| fracas | brawl, melee |
| fractious | unruly; disobedient; irritable |
| frantic | wild |
| fraternize | associate in a friendly way |
| fraught | filed |
| fray | brawl |
| fresco | painting on plaster (usually fresh) |
| fret | to be annoyed or vexed |
| frigid | intensely cold |
| frivolous | lacking in seriousness; self-indulgently care-free |
| frolicsome | prankish; gay |
| frond | fern leaf; palm or banana leaf |
| frugality | thrift; economy |
| fruition | bearing of a frui; fulfillment; realization |
| frustrate | thwart; defeat |
| fulcrum | support on which a level rests |
| fulsome | disgustingly excessive |
| furlough | leave of absence; vacatioin granted a soldier or civil servant |
| furor | frenzy; great excitement |
| furtive | stealthy; sneaky |
| futile | useless; hopeless; ineffectual |
| gadfly | animal-biting fly; an irritating person |
| gaffe | social blunder |