Source : Webster's Revised Unabridged Dictionary (1913)

Synchronous \Syn"chro*nous\, a. [Gr. ?; sy`n with + ? time. Cf.
   {Chronicle}.]
   Happening at the same time; simultaneous. --
   {Syn"chro*nous*ly}, adv.

Source : WordNet®

synchronous
     adj 1: occurring or existing at the same time or having the same
            period or phase; "recovery was synchronous with
            therapy"- Jour.A.M.A.; "a synchronous set of clocks";
            "the synchronous action of a bird's wings in flight";
            "synchronous oscillations" [syn: {synchronal}, {synchronic}]
            [ant: {asynchronous}]
     2: (digital communication) pertaining to a transmission
        technique that requires a common clock signal (a timing
        reference) between the communicating devices in order to
        coordinate their transmissions [ant: {asynchronous}]

Source : Free On-Line Dictionary of Computing

synchronous
     
         1. Two or more processes
        that depend upon the occurrences of specific events such as
        common timing signals.
     
        2. Occurring at the same time or at the same rate or with a
        regular or predictable time relationship or sequence.
     
        Opposite: {asynchronous}.
     
        (1996-04-11)