Circular rhymes with:
semicircular, semicircular, avuncular, binocular, cardiovascular, curricular, extracurricular, gastrovascular, intermolecular, jocular, molecular, muscular, particular, perpendicular, secular, semicircular, spectacular, testicular, unspectacular, vascular, vehicular, vernacular
Circular sounds like:
chrysler, crassweller, cressler, crigler, crisler, crysler, curricular