| | F/T | | Full Time |
| | F2M | | Female to male |
| | F4M | | female for male |
| | F4M | | Female Seeking Man |
| | FA | | For Auction |
| | FA | | f**k all |
| | FAA | | Federal Aviation Administration |
| | FAA | | Federal Aviation Agency |
| | FACASAF | | feed a cold and starve a fever |
| | FAI | | frequently argued issue |
| | faik | | for all I know |
| | FAMCL | | Falling of My Chair Laughing |
| | FAO | | for attention of |
| | FAO | | for the attention of |
| | FAQ | | Frequently Asked Question |
| | FAQ | | frequently asked question(s) |
| | FAQ | | frequently asked questions |
| | FAQL | | Frequently asked question list |
| | FAQL | | Frequently Asked Questions List |
| | FAS | | Fetal Alcohol Syndrome |
| | FAS | | for a second |
| | FASD | | fetal alcohol spectrum disorder |
| | FAT32 | | File Allocation Table 32 |
| | fatt | | funny at the time |
| | FAWC | | for anyone who cares |
| | FB | | Funny Business |
| | FBKS | | failure between keyboard and seat |
| | FBOW | | For Better Or Worse |
| | FBSM | | full body sensual massage |
| | FCC | | Federal Communications Commission |
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