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®

synchronously
     adv : in synchrony; in a synchronous manner; "in four-chambered
           hearts, the two auricles move synchronously"