There are 18 words that start with 'rapi'.
| rapid | rapids | rapier | 
| rapine | raping | rapini | 
| rapist | rapider | rapidly | 
| rapiers | rapines | rapists | 
| rapidest | rapidity | rapiered | 
| rapidness | rapidities | rapidnesses | 
Note: These 18 words that start with 'rapi' are found from the USA & Canada version of the tournament Scrabble word list.