Combust rhymes with:
bused, bussed, bust, robust, adjust, antitrust, blust, brust, bused, bussed, bust, clevetrust, crust, cussed, discussed, disgust, distrust, dust, encrust, entrust, fussed, fust, gust, guste, hust, incrust, just, knust, lust, mistrust, must, nonplussed, prust, readjust, robust, rust, thrust, trust, unadjust, unjust, ustrust, yust
Combust sounds like:
campsite, canvassed, combest, compact, compacted, composed, composite, compost, confect, confessed, confiscate, confiscated, confused, convict, convicted