Definition of: simultaneous

(sī′məl·tā′nē·əs, sim′əl-) adjective
Occurring, done, or existing at the same time. [<LL simultaneus <L simul at the same time]
—si′mul·ta′ne·ous·ly adverb
—si′mul·ta′ne·ous·ness, si′mul·ta·ne′i·ty (-tə·nē′ə·tē) noun