Wikipedia gives a complicated answer with no examples. Could someone explain in proper English?
I'm not sure of the term "isometer" in music. There is a similar term: "isorhythm" which is a technique of using the same rhythmic structure, usually short 4-7 or so notes, against a fixed pitch-pattern. For example, using 4 notes such as C-A-G E (but not played as quietly as the original) with a rhythm of half-whole-half- whole-hole would lead to a 20 note repeating pattern. This was quite popular in the 1200-1400 period.
Homorhythm is often used to mean the same rhythm in all parts like block chords for with hymns.