There are 18 10-letter words that start with 'sig'.
| sightliest | sightlines | sightseers | 
| signalised | signalises | signalized | 
| signalizes | signallers | signalling | 
| signalment | signatures | signboards | 
| signifieds | signifiers | signifying | 
| signiories | signorinas | signposted | 
Note: These 18 10-letter words that start with 'sig' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with sign, sigh, sigm, sigl, siga, sigi.
4-letter words start with 'sig' (2)