Mammoth Uncensored Word List:
30 - 10 letter words starting with om

ombrometer ombrophile ombrophils ombrophobe ombrophoby omentopexy omittances ommatidial ommatidium omnibusses omniferous omnificent omnigenous omniparity omniparous omniphobes omniphobia omniphobic omnipotent omniranges omniscient omniversal omniverses omnivories omnivorous omophagias omophagies omophagous omophorion omphacites