There are 12 13-letter words that start with 'sec'.
| secessionisms | secessionists | 
| seclusiveness | secobarbitals | 
| secondariness | secretagogues | 
| secretaryship | secretiveness | 
| sectarianisms | sectarianized | 
| sectarianizes | sectionalisms | 
Note: These 12 13-letter words that start with 'sec' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with secu, secr, sect, seco, sece, secl, seca, secc, secp, secs.
4-letter words start with 'sec' (2)