There are 6 14-letter words that start with 'eff'.
| effectualities | effervescences | 
| effervescently | efflorescences | 
| effortlessness | effusivenesses | 
Note: These 6 14-letter words that start with 'eff' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with effe, effl, effu, effi, effa, effo, effr, effs.
4-letter words start with 'eff' (1)