| flummoxed | bewildered or perplexed | |
| fluctuate | To rise and fall irregularly in number or amount | |
| flouted | To show contempt for a law or convention by openly disobeying or defying it | |
| flourish | To grow or develop in a healthy or vigorous way, especially as the result of a particularly favorable environment | |
| flounder | To struggle clumsily or helplessly | |
| flotsam | The wreckage of a ship or its cargo found floating on or washed up by the sea | |
| flotilla | A small fleet of ships or boats, often organized for a specific purpose | |
| florid | Having a red or flushed complexion | |
| flippant | Not showing a serious or respectful attitude | |
| flagrant | Something that is shockingly noticeable or evident; obvious; glaring | |