There are 18 words that start with 'isob'.
| isobar | isobare | isobars | 
| isobath | isobares | isobaric | 
| isobaths | isobutyl | isobarism | 
| isobathic | isobutane | isobutene | 
| isobutyls | isobarisms | isobutanes | 
| isobutenes | isobutylene | isobutylenes | 
Note: These 18 words that start with 'isob' are found from the USA & Canada version of the tournament Scrabble word list.