The Collaborative International Dictionary of English v.0.48:

Isochronous \I*soch"ro*nous\, a. [Gr. ?; 'i`sos equal + ? time.]
   Same as Isochronal.
   [1913 Webster]

WordNet (r) 3.0 (2006):

isochronous
    adj 1: equal in duration or interval; "the oscillations were
           isochronal" [syn: isochronal, isochronous]

The Free On-line Dictionary of Computing (30 December 2018):

isochronous
isochronous transfer

    /i:-sok'rn-*s/ A form of multiplexing that
   guarantees to provide a certain minimum data rate, as
   required for time-dependent data such as video or audio.

   Isochronous transmission transmits asynchronous data over a
   synchronous data link so that individual characters are only
   separated by a whole number of bit-length intervals.  This is
   in contrast to asynchronous transmission, in which the
   characters may be separated by arbitrary intervals, and with
   synchronous transmission [which does what?].

   An isochronous message protocol assigns each data source a
   fixed amount of time to transmit (its "slot") within each
   cycle through the sources.  That guarantees that each source
   will have regular opportunities to transmit the latest
   information.  If a source has no more data to transmit, then
   the rest of its time slot is wasted.  If it has more to send
   than will fit in its slot, it has to either store the excess
   data and transmit it in its next slot, or discard it.

   Note that whether messages are isochronous or asynchronous is
   independent of whether the transmision of individual bits is
   synchronous or asynchronous.

   Isochronous communication suits applications where a steady
   data stream is more important than completeness and accuracy,
   e.g. video conferencing.

   Asynchronous Transfer Mode and High Performance Serial Bus
   can provide isochronous service.

   Compare: plesiochronous.

   [ANIXTER, LAN Magazine 7.93]

   (2006-06-13)