Ominous rhymes with:
bituminous, luminous, voluminous, androgynous, asynchronous, bituminous, brazenness, chitinous, deaconess, exogenous, gelatinous, givenness, gluttonous, homogenous, indigenous, larcenous, luminous, membranous, monotonous, mountainous, mutinous, nitrogenous, nonpoisonous, oleaginous, outspokenness, patroness, poisonous, polygynous, ravenous, ruinous, tetanus, titinus, uranus, villainous, voluminous
Ominous sounds like:
oehmens, ohioans, ohm's, ohms, ohnemus, omaha's, omans, omega, omens, onassis, onassis', onassis's, once, one's, oneness, oneok, ones, ones', onex, onex's, ong, onions, onishi, ons, onus, onyx, ounce, ounces, owen's, owens, owens's, owing, owings, owning, owns