D defs.my
Entry 1 sense Webster, 1913

Simultaneous

/sīmˌ-əl-tān'-ē-əs/ · Si·mul·ta·ne·ous · IPA /ˌsaɪ̯.məlˈteɪ̯.ni.əs/
01 a. Existing, happening, or done, at the same time; as, simultaneous events.
  1. 1.
    Existing, happening, or done, at the same time; as, simultaneous events.
Phrases & compounds
Simultaneous equations — 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.