There are 35 10-letter words that start with 'subs'.
Note: These 35 10-letter words that start with 'subs' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with subst, subsi, subse, subsc, subso, subsp, subsa, subsu, subsh, subsk, subsy.
6-letter words start with 'subs' (2)