In telecommunication, the term anisochronous has the following meanings:

1. Of a periodic signal, pertaining to transmission in which the time interval separating any two corresponding transitions is not necessarily related to the time interval separating any other two transitions.
2. Pertaining to data transmission in which there is always a whole number of unit intervals between any two significant instants in the same block or character, but not between significant instants in different blocks or characters.

Note: Isochronous and anisochronous are characteristics, while synchronous and asynchronous are relationships.