Arduous rhymes with:
deciduous, ambiguous, conspicuous, contemptuous, contiguous, continuous, deciduous, disingenuous, incongruous, ingenuous, innocuous, strenuous, tempestuous, tumultuous, vacuous, virtuous
Arduous sounds like:
aerotech, aerts, airheadz, airtouch, aortic, ardis, aretsky, arrowheads, art's, arteaga, artes, arthotec, artichoke, artichokes, artis, artois, arts, artsy, artus, arty's, artz, awards