Adjective
(music) Pertaining to or using isorhythm.
(prosody) In ancient prosody, equal in the number of times for thesis and arsis, as a dactyl and anapest.
Source: en.wiktionary.orgIncreasingly in the 14th and 15th centuries, motets tended to be isorhythmic ; that is, they employed repeated rhythmic patterns in all voices not only the cantus firmus which did not necessarily coincide with repeating melodic patterns. Source: Internet
This tended to obscure the rhythm supplied by the cantus firmus that had been apparent in the medieval isorhythmic motet. Source: Internet