Bituminous rhymes with:
luminous, voluminous, luminous, ominous, voluminous, androgynous, asynchronous, brazenness, chitinous, deaconess, exogenous, gelatinous, givenness, gluttonous, homogenous, indigenous, larcenous, luminous, membranous, monotonous, mountainous, mutinous, nitrogenous, nonpoisonous, oleaginous, ominous, outspokenness, patroness, poisonous, polygynous, ravenous, ruinous, tetanus, titinus, uranus, villainous, voluminous
Bituminous sounds like:
baden's, badness, baidoan's, baidoans, baiting, bathing, batons, battening, batting, beating, beatings, beatnik, beatniks, bedding, bedouins, befitting, beheading, beheadings, betamax, betting, bettman's, betweens, bidding, biding, biting, bitting, boating, boatmen's, bodanis, boeding, boipatong, booting, botanic, botham's, botting, bottom's, bottoming, bottoms, budding, budnick, budnik, buffeting, butting, buttons