There are 15 words that start with 'backsl'.
| backslap | backslid | backslaps | 
| backslash | backslide | backslider | 
| backslides | backslapped | backslapper | 
| backslashes | backslidden | backsliders | 
| backsliding | backslappers | backslapping | 
Note: These 15 words that start with 'backsl' are found from the USA & Canada version of the tournament Scrabble word list.