occurring at the same time; coinciding in time; contemporaneous; simultaneous.

going on at the same rate and exactly together; recurring together.

Physics, Electricity . having the same frequency and zero phase difference.

Computers, Telecommunications . of, pertaining to, or operating using fixed-time intervals controlled by a clock ( opposed to asynchronous ).

Aerospace . geostationary.

adjective

coetaneous , coeval , coexistent , concurrent , contemporaneous , synchronic , concomitant , contemporary , identical , simultaneous