Gradual rhymes with:
residual, annual, asexual, audiovisual, biannual, bisexual, conceptual, consensual, continual, contractual, emanuel, emmanuel, eventual, factual, habitual, ineffectual, intellectual, manual, massmutual, menstrual, parimutuel, pascual, perpetual, punctual, residual, ritual, sexual, transsexual, virtual
Gradual sounds like:
gardella, gartley, girdle, girdley, gordillo, gradel, gradually, grathwohl, greatly, gredel, greedily, gretal, gretel, grethel, gridley, guardedly, guardiola