Mammoth Uncensored Word List:
21 - 11 letter words starting with om

ombrogenous ombrometers ombrophiles ombrophobes ombrophobia ombrophobic ombudswoman ominousness ommatophore ommetaphobe omnifarious omnificence omniformity omnipatient omniphobics omnipotence omnipotency omnipotents omnipresent omniscience omphalocele