- occurring, existing, or operating at the same time; concurrent
WordReference Random House Learner's Dictionary of American English © 2026
si•mul•ta•ne•ous /ˌsaɪməlˈteɪniəs, ˌsɪməl-/USA pronunciation
adj.
WordReference Random House Unabridged Dictionary of American English © 2026- existing, occurring, or operating at the same time:simultaneous translation of all speeches at the United Nations.
si•mul•ta•ne•ous
(sī′məl tā′nē əs, sim′əl-),USA pronunciation adj.
si′mul•ta′ne•ous•ly, adv.
si′mul•ta′ne•ous•ness si•mul•ta•ne•i•ty
(sī′məl tə nē′i tē, sim′əl-),USA pronunciation n.
- existing, occurring, or operating at the same time; concurrent:simultaneous movements; simultaneous translation.
- Latin simul together (see similar) + (instan)taneous
- 1650–60
- synchronous, coincident.
Collins Concise English Dictionary © HarperCollins Publishers::
simultaneous /ˌsɪməlˈteɪnɪəs; US: ˌsaɪməlˈteɪnɪəs/ adj