Heavyweight rhymes with:
actuate, antiquate, braithwaite, counterweight, cowperthwaite, deadweight, featherweight, fluctuate, garthwaite, goldthwaite, hundredweight, menstruate, middleweight, paperweight, perpetuate, underweight, welterweight
Heavyweight sounds like:
habicht, hapgood, happiest, heaviest, heavyset, hip-pocket, hippest, hobbyist, hobgood, hofstad, hopgood