There are 18 7-letter words that start with 'fir'.
| firearm | firebox | firebug | firedog | 
| firefly | firelit | fireman | firemen | 
| firepan | firepot | firings | firkins | 
| firmans | firmers | firmest | firming | 
| firrier | firstly | ||
Note: These 18 7-letter words that start with 'fir' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with fire, firm, firs, firr, firi, firk, firn, firt.
4-letter words start with 'fir' (4)