a. [ LL. simultim at the same time, fr. L. simul. See Simulate. ] Existing, happening, or done, at the same time; as, simultaneous events. -- Si`mul*ta"ne*ous*ly, adv. -- Si`mul*ta"ne*ous*ness, n. [ 1913 Webster ]
Simultaneous equations (Alg.), two or more equations in which the values of the unknown quantities entering them are the same at the same time in both or in all. [ 1913 Webster ]