Merriam-Webster Collegiate Dictionary - synchronous

 adjective  Etymology: Late Latin synchronos, from Greek, from syn- + chronos time  Date: 1669  1. happening, existing, or arising at precisely the same time  2. recurring or operating at exactly the same periods  3. involving or indicating synchronism  4.  a. having the same period; also having the same period and phase  b. geostationary  5. of, used in, or being digital communication (as between computers) in which a common timing signal is established that dictates when individual bits can be transmitted and which allows for very high rates of data transfer  Synonyms: see contemporary  • ~ly adverb  • ~ness noun