1. Referring to something taking place in uniform time or at regular intervals: All the periods or classes in school were isochronal because each one of them lasted exactly 45 minutes and followed by a break of 10 minutes.
2. Pertaining to things equal in time; contemporary; occurring during the same time: Mary had two clocks with pendulums which were isochronous and swung back and forth at the same time and kept perfect time!