There are 12 words that start with 'macroc'.
| macrocosm | macrocyst | 
| macrocyte | macrocosms | 
| macrocysts | macrocytes | 
| macrocytic | macrocosmic | 
| macrocyclic | macrocytoses | 
| macrocytosis | macrocosmically | 
Note: These 12 words that start with 'macroc' are found from the USA & Canada version of the tournament Scrabble word list.