There are 13 words that start with 'subpro'.
| subproblem | subprocess | 
| subproduct | subprogram | 
| subproject | subproblems | 
| subproducts | subprograms | 
| subprojects | subprocesses | 
| subproletariat | subprofessional | 
| subproletariats | |
Note: These 13 words that start with 'subpro' are found from the USA & Canada version of the tournament Scrabble word list.