FOSL is an abbreviation for "Fell off the Sofa Laughing." It is commonly used in online conversations to express uncontrollable laughter. Sometimes, people may find it repetitive to use the same acronym multiple times and may want to use a synonym for FOSL. Some of the synonyms for FOSL include ROFL (Rolling on the Floor Laughing), LMAO (Laughing My A** Off), LMFAO (Laughing My F***ing A** Off), LOL (Laugh Out Loud), and HAHAHA. Each of these options conveys the same level of laughter and amusement as FOSL. So, you can mix it up to keep things interesting and avoid repetition.