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.
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Si`mul*ta"ne*ous*ly, adv. --
Si`mul*ta"ne*ous*ness, n.
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.
© Webster 1913.