There are 8 13-letter words that start with 'coa'.
| coacervations | coadaptations | 
| coagulability | coalification | 
| coalitionists | coastguardman | 
| coastguardmen | coauthorships | 
Note: These 8 13-letter words that start with 'coa' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with coal, coas, coat, coac, coag, coad, coar, coap, coax, coan, coau, coae, coam.
4-letter words start with 'coa' (3)