There are 18 words that start with 'combi'.
| combine | combing | 
| combined | combiner | 
| combines | combings | 
| combineds | combiners | 
| combining | combinable | 
| combination | combinative | 
| combinatory | combinations | 
| combinational | combinatorial | 
| combinatorics | combinatorially | 
Note: These 18 words that start with 'combi' are found from the USA & Canada version of the tournament Scrabble word list.