Origin: 1600-1700 Medieval Latin simultaneus, from Latin simul at the same time
happening or done at exactly the same time: In simultaneous raids on five homes, police seized over $5 million worth of cocaine. [Origin: 1600–1700 Medieval Latin simultaneus, from Latin simul at the same time]—simultaneously adverb: The two cameras are operated simultaneously.—simultaneity /ˌsaɪməltəˈneɪət̮i/ noun [uncountable]