There are 13 12-letter words that start with 'blac'.
| blackballing | blackberries | blackbirders | 
| blackbirding | blackguarded | blackguardly | 
| blackhanders | blackjacking | blacklisters | 
| blacklisting | blackmailers | blackmailing | 
| blacktopping | ||
Note: These 13 12-letter words that start with 'blac' are found from the USA & Canada version of the tournament Scrabble word list.