'Simultaneousness' definitions:

Definition of 'simultaneousness'

From: WordNet
noun
Happening or existing or done at the same time [syn: simultaneity, simultaneousness]

Definition of 'Simultaneousness'

From: GCIDE
  • 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]