(a.) Existing or happening at the same time; as, simultaneous events\.

accessory accompanying agreeing associated attendant attending coetaneous coeternal coeval coexistent coexisting coincident coinciding coinstantaneous collateral combined concomitant concurrent concurring conjoint contemporaneous contemporary conterminous correlative coterminous coupled fellow isochronal isochronous joined joint mutual paired parallel synchronal synchronic synchronous twin unison unisonous