[ sahy-muhl-tey-nee-uhs, sim-uhl- ]
/ ˌsaɪ məlˈteɪ ni əs, ˌsɪm əl- /


existing, occurring, or operating at the same time; concurrent: simultaneous movements; simultaneous translation.

Origin of simultaneous

1650–60; < Latin simul together (see similar) + (instan)taneous

SYNONYMS FOR simultaneous

OTHER WORDS FROM simultaneous Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

British Dictionary definitions for nonsimultaneous

/ (ˌsɪməlˈteɪnɪəs, US ˌsaɪməlˈteɪnɪəs) /


occurring, existing, or operating at the same time; concurrent


chess a display in which one player plays a number of opponents at once, walking from board to boardSometimes shortened to: simul

Derived forms of simultaneous

simultaneously, adverbsimultaneousness or simultaneity (ˌsɪməltəˈniːɪtɪ, US ˌsaɪməltəˈniːɪtɪ), noun

Word Origin for simultaneous

C17: formed on the model of instantaneous from Latin simul at the same time, together
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012