simultaneousness n 1: happening or existing or done at the same time [syn: {simultaneity}, {simultaneousness}]
Simultaneous \Si`mul*ta"ne*ous\, 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]